Semiconductor light emitting device substrate including an uneven structure having convex portions, and a flat surface therebetween

ABSTRACT

A semiconductor light emitting device substrate including an uneven structure on one surface, the uneven structure including numerous convex portions and a flat surface between the convex portions, and multiple areas in which the central portions of seven adjacent convex portions are continuously and positionally aligned to become six vertices and intersection points of diagonal lines of a regular hexagon, and the area, shape and lattice orientation of the plurality of areas are random. A semiconductor light emitting device including the semiconductor light emitting device substrate; and a semiconductor functional layer laminated on the semiconductor light emitting device substrate.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application No. PCT/JP2013/072296, filed Aug. 21, 2013,designating the U.S., and published in Japanese as WO 2014/030670 onFeb. 27, 2014, which claims priority to Japanese Patent Application No.2012-182302, filed Aug. 21, 2012; and Japanese Patent Application No.2013-126025, filed Jun. 14, 2013, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a semiconductor light emitting devicesubstrate, a semiconductor light emitting device and methods ofmanufacturing these. In particular, the present invention relates to asemiconductor light emitting device substrate suitable for a groupnitride semiconductor light emitting device, a semiconductor lightemitting device using a substrate obtained by the aforementioned method,and methods of manufacturing these.

Priority is claimed on Japanese Patent Application No. 2012-182302,filed Aug. 21, 2012, and Japanese Patent Application No. 2013-126025,filed Jun. 14, 2013, the contents of which are incorporated herein byreference.

BACKGROUND ART

Semiconductor light emitting devices are used either as an ultraviolet-,blue- or green light emitting diode element, or as an ultraviolet-,blue- or green laser diode element. In particular, group III-V nitridesemiconductor light emitting devices having a light emitting layercomposed of a group nitride semiconductor that uses nitrogen as a groupV element are widely used.

A semiconductor light emitting device substrate for supporting thislight emitting structure is formed of sapphire, silicon carbide, siliconor the like, and usually has a lower refractive index than that of asemiconductor layer or the like that constitutes the light emittingstructure.

A group III-V nitride semiconductor light emitting device has a basicstructure in which an n-type semiconductor layer, a light emitting layerand a p-type semiconductor layer are laminated sequentially on asubstrate made of sapphire or the like, and an n-type electrode and ap-type electrode are formed on the n-type semiconductor layer and on thep-type semiconductor layer, respectively. Then, light emitted in thelight emitting layer is extracted from the p-type electrode side and/orthe substrate side.

A portion of light generated by the light emitting structure is totallyreflected repeatedly between the semiconductor light emitting devicesubstrate and the light emitting structure in accordance with thedifference in the refractive indices between the semiconductor lightemitting device substrate and the light emitting structure. As a result,the light generated by the light emitting structure is attenuated insidethe light emitting structure.

In order to solve this problem, by laminating the semiconductor layerafter forming an uneven structure on the substrate in advance, variousmethods have been proposed for changing the light angle to suppress thetotal reflection by using the uneven structure of the aforementioneduneven substrate, thereby improving the light extraction efficiency (seePatent Documents 1 to 3 and Non-Patent Document 1).

For example, in Patent Documents 1 and 2, it has been proposed to form amask pattern on a substrate using a photolithography method, form anuneven structure on the substrate by dry etching the aforementionedsubstrate using the mask pattern, and then form a semiconductor layer onthe uneven structure.

In addition, in Patent Document 3, it has been proposed to form anuneven structure on a substrate by dry etching the aforementionedsubstrate using inorganic particles arranged on the substrate as anetching mask, and then form a semiconductor layer on the unevenstructure. In Patent Document 3, as a preferred method of arranginginorganic particles on a substrate, a method has been proposed in which,using a slurry prepared by dispersing inorganic particles in a mediumsuch as water, the aforementioned substrate is immersed in theaforementioned slurry, or the aforementioned slurry is applied orsprayed on the aforementioned substrate followed by drying. In addition,in order to form a favorable semiconductor layer, it has been acceptedthat inorganic particles should be arranged on the substrate with acoverage of 90% or less.

Further, in Non-Patent Document 1, studies have been made on therelationship between the pitch of an uneven structure to be formed on asubstrate and the effect of improving light extraction efficiency. Inaddition, it has been described that the effect of improving the lightextraction efficiency was hardly achieved by an uneven structure with apitch of 1,000 nm, whereas 170% of light extraction efficiency wasachieved by an uneven structure with a pitch of 500 nm, as compared tothe case of using a flat substrate.

It should be noted that as a method of producing a fine structure havingan uneven structure with a pitch of 1 μm or less, an electron beamlithography method, an interference exposure method and the like havebeen known conventionally.

CITATION LIST Patent Documents

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2002-280611

[Patent Document 2] Japanese Unexamined Patent Application, FirstPublication No. 2003-318441

[Patent Document 3] Japanese Unexamined Patent Application, FirstPublication No. 2007-19318

Non-Patent Document

[Non-Patent Document 1] Taku Shinagawa, Yuki Abe, Hiroyuki Matsumoto,BoCheng Li, Kazuma Murakami, Narihito Okada, Kazuyuki Tadatomo, MasatoKannaka, and Hideo Fujii, Light-emitting diodes fabricated onnanopatterned sapphire substrates by thermal lithography, 2010 WILEY-VCHVerlag GmbH & Co. KGaA, Weinheim

SUMMARY OF INVENTION Technical Problem

However, according to the method of Patent Documents 1 and 2, there hasbeen a problem of increase in cost due to an increase in the number ofphotolithography steps. In addition, the fine uneven structure of thesemiconductor light emitting device substrate is constituted of a numberof convex portions that are arranged on a surface on which the lightemitting structure is formed. The more the number of convex portions inthe fine uneven structure and the smaller the intervals between theconvex portions in the fine uneven structure, the higher the effect ofsuppressing the total reflection. The fine uneven structure of thesemiconductor light emitting device substrate is formed by dry etchingthe light emitting structure forming surface as described in PatentDocuments 1 and 2, for example, and the mask used in the dry etching isformed by photolithography. At this time, since there is a limit inreducing the size of the mask, naturally, there is also a limit inminiaturization of the uneven structure. As shown in Non-Patent Document1, although it has been desired to make the pitch of the unevenstructure 1 μm or less, production of pitches of several micrometers isthe limit by laser lithography which is a practical photolithographytechnique. Therefore, with the method of Patent Documents 1 and 2, ithas been difficult to achieve a sufficient light extraction efficiency.

On the other hand, for this reason, in terms of enhancing the extractionefficiency of light generated by the light emitting structure, even withthe fine uneven structure described above, there is still a room forimprovement.

In addition, due to the effect of diffraction light, problems in thesemiconductor light emitting device, such as the color shift and thedifferent radiation intensity (high in-plane anisotropy) depending onthe viewing angle, have occurred in some cases.

Furthermore, when a substrate with low flatness is used, since a resisttends to become thick at the recess portion of the substrate, variationsoccur in the time required until the disappearance of the mask duringetching, as a result of which variations occur in the height and shapeof the uneven structure and a sufficient light extraction efficiencycannot be achieved. In addition, if an etching mask prepared bynanoimprinting was applied on a substrate with low flatness, anon-patterned portion (planned) was contaminated by the residual resistfilm, which was also a problem.

For this reason, in preparing a semiconductor light emitting devicesubstrate by conventional photolithography, it has been necessary to usea substrate with high flatness. However, there has been a problem that asubstrate with high flatness, especially a sapphire substrate with highflatness could not be obtained without a high level of polishingtechnique, and was thus very expensive.

In addition, according to the electron beam lithography method orinterference exposure, although a fine structure with a pitch of unevenpatterns of 1 μm or less can be produced, it is not suited forprocessing substrates with a large area of about φ2 inches to φ6 inches,such as the semiconductor light emitting device substrate.

In other words, the electron beam lithography method has a slow drawingspeed that takes about two weeks to draw 1 inch, and requires aconsiderable amount of cost and time for the processing of substrateswith a large area. In addition, it is difficult to maintain theenvironment (voltage, vibration, air temperature and the like)constantly during the drawing of a large area over a long period oftime, and thus production of a uniform fine structure is difficult.

Further, in the interference exposure method, a Gaussian beam is used asa light source, and an appropriate exposure time would be different atthe central portion and at the peripheral portion if the area of theexposure target increases. In addition, it is sensitive to vibration(vibration of ground and building, vibration of air and the like), andthe image is blurred to lower the resolution if subjected to theslightest vibration during the exposure time. For this reason,production of a uniform fine structure with a large area is difficult.

The electron beam lithography method and interference exposure methodrequire large and expensive apparatuses, which is also a factor ofpreventing industrial applications.

In addition, with the method of Patent Document 3 for disposinginorganic particles on a substrate using a slurry prepared by dispersingthe inorganic particles in a medium such as water, the inorganicparticles easily overlap in many layers, which makes it difficult toproduce an etching mask with a uniform thickness. Even if the amount ofinorganic particle used is reduced to an extent for covering 90% or lessof the substrate, it is difficult to avoid partial overlapping.

Furthermore, as a result of the studies conducted by the inventors ofthe present invention, it has been discovered that even if the partialoverlapping was avoided, inorganic particles are brought into contactwith each other at numerous locations, and the substrate at thoselocations was etched so that the cross sections thereof were asubstantially inverted triangular shape. The presence of a flat bottomsurface at the recess portion is required for the epitaxial growth ofthe semiconductor layer on a substrate. For this reason, there was aconcern of crystal defects being generated in the semiconductor layerwith the method of Patent Document 3.

An aspect of the present invention is made in view of theabove-mentioned circumstances and has an object of providing asemiconductor light emitting device with which a sufficient lightextraction efficiency can be achieved and also the problems of increasesin the color shift and in-plane anisotropy are prevented.

In addition, another aspect of the present invention has an object ofproviding a semiconductor light emitting device substrate capable offorming a semiconductor layer with few crystal defects and suitable forthe manufacture of a semiconductor light emitting device that solves theabove problems.

Further, yet another aspect of the present invention has an object ofproviding a method of manufacturing a semiconductor light emittingdevice substrate which is capable of manufacturing a semiconductor lightemitting device substrate that solves the above problems, and is alsocapable of forming an uneven structure with a pitch of 1 μm or less by asimple method at low cost and in a short period of time.

Moreover, yet another aspect of the present invention has an object ofproviding a method of manufacturing a semiconductor light emittingdevice capable of manufacturing a semiconductor light emitting devicethat solves the above problems, by using the method of manufacturing asemiconductor light emitting device substrate that solves the aboveproblems.

Solution to Problem

In order to achieve the above objects, some aspects of the presentinvention employ the following configurations.

[1] A method of manufacturing a semiconductor light emitting devicesubstrate characterized by including:

a particle arranging step for arranging a plurality of particles in asingle layer on a substrate so that an arrangement deviation D(%)defined by a formula (1) shown below is not greater than 15%;

a particle etching step for dry etching the aforementioned plurality ofparticles arranged to provide a void between the particles in acondition by which the aforementioned particles are etched while theaforementioned substrate is not etched substantially; and

a substrate etching step for dry etching the aforementioned substrate byusing the plurality of particles after the aforementioned particleetching step as an etching mask, thereby forming an uneven structure onone side of the aforementioned substrate:D[%]=|B−A|×100/A  (1)

with a proviso that in formula (1), A denotes an average particlediameter of particles, B denotes a most frequent pitch betweenparticles; and |B−A| denotes an absolute value of difference between Aand B.

[2] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [1],

wherein the aforementioned particle arranging step includes:

a dropping step for dropwise adding a dispersion liquid in whichparticles are dispersed in a solvent having a smaller specific gravitythan water to a liquid surface of water inside a water tank;

a monolayer particle film forming step for forming a monolayer particlefilm composed of the aforementioned particle on a liquid surface ofwater by vaporizing the aforementioned solvent; and

a transferring step for transferring the aforementioned monolayerparticle film onto a substrate.

[3] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [1] or [2],

wherein a most frequent pitch between the aforementioned particles isnot greater than 5 μm.

[4] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [1] or [2],

wherein a most frequent pitch between the aforementioned particles isnot greater than 1 μm.

[5] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [1] or [2],

wherein a most frequent pitch between the aforementioned particles isfrom 200 nm to 700 nm.

[6] The method of manufacturing a semiconductor light emitting devicesubstrate according to any one of the aspects [1] to [5],

wherein the aforementioned substrate is sapphire, the aforementionedparticles are silica, the aforementioned particle etching step is a stepof using at least one type of gas selected from the group consisting ofCF₄, SF₆, CHF₃, C₂F₆, C₃F₈, CH₂F₂, O₂ and NF₃ as an etching gas, and theaforementioned substrate etching step is a step of using at least onetype of gas selected from the group consisting of Cl₂, Br₂, BCl₃, SiCl₄,HBr, HI, HCl and Ar as an etching gas.

[7] A method of manufacturing a semiconductor light emitting devicesubstrate characterized by including:

a particle arranging step for arranging a plurality of particles in asingle layer on a substrate;

a particle etching step for dry etching the aforementioned plurality ofparticles arranged to provide a void between the particles in acondition by which the aforementioned particles are etched while theaforementioned substrate is not etched substantially; and

a substrate etching step for dry etching the aforementioned substrate byusing the plurality of particles after the aforementioned particleetching step as an etching mask, thereby forming an uneven structure onone side of the aforementioned substrate,

wherein the aforementioned substrate is sapphire, the aforementionedparticles are silica, the aforementioned particle etching step is a stepof using at least one type of gas selected from the group consisting ofCF₄, SF₆, CHF₃, C₂F₆, C₃F₈, CH₂F₂, O₂ and NF₃ as an etching gas, and

-   -   the aforementioned substrate etching step is a step of using at        least one type of gas selected from the group consisting of Cl₂,        Br₂, BCl₃, SiCl₄, HBr, HI, HCl and Ar as an etching gas.

[8] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [7],

wherein the aforementioned particle arranging step includes:

a dropping step for dropwise adding a dispersion liquid in whichparticles are dispersed in a solvent having a smaller specific gravitythan water to a liquid surface of water inside a water tank;

a monolayer particle film forming step for forming a monolayer particlefilm composed of the aforementioned particle on a liquid surface ofwater by vaporizing the aforementioned solvent; and

a transferring step for transferring the aforementioned single particlefilm onto a substrate.

[9] The method of manufacturing a semiconductor light emitting devicesubstrate according to any one of the aspects [1] to [8],

wherein an absolute difference (TTV) between a maximum thickness and aminimum thickness of the aforementioned substrate as defined by ASTMF657 is from 5 μm to 30 μm,

a difference (WARP) between a maximum value and a minimum value ofdeviation from a reference plane as defined by ASTM F1390 is from 10 μmto 50 μm, and

an absolute value (|BOW|) of a distance from a reference plane at acentral portion of the substrate as defined by ASTM F534.3.1.2 is from10 μm to 50 μm.

[10] A method of manufacturing a semiconductor light emitting devicesubstrate, the method including:

a particle arranging step for arranging a plurality of particles in asingle layer on an upper surface of a substrate to forma monolayerparticle film;

a particle etching step for dry etching the aforementioned plurality ofparticles arranged to provide a void between the particles in acondition by which the aforementioned particles are etched while theaforementioned substrate is not etched substantially; and

a substrate etching step for etching the aforementioned upper surface byusing the aforementioned monolayer particle film as a mask,

wherein in the aforementioned substrate etching step,

a step is formed in a region that is exposed in the upper surface of theaforementioned substrate after the aforementioned particle etching step.

[11] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [10],

wherein in the aforementioned particle etching step, a size of each ofthe aforementioned plurality of particles is reduced.

[12] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [10] or [11],

wherein in the aforementioned substrate etching step,

of the plurality of particles, the larger a void between two particles,the smaller the aforementioned step.

[13] The method of manufacturing a semiconductor light emitting devicesubstrate according to the aspect [12],

wherein in the aforementioned particle arranging step, theaforementioned plurality of particles are arranged by an LB method.

[14] A method of manufacturing a semiconductor light emitting device,the method including:

a step of forming a semiconductor light emitting device substrate by themethod of manufacturing a semiconductor light emitting device substratedescribed in any one of the aspects [10] to [13]; and

a step of forming a light emitting structure including a semiconductorlayer on the aforementioned upper surface where the aforementioned stepis formed in the aforementioned semiconductor light emitting devicesubstrate.

[15] A method of manufacturing a semiconductor light emitting device,the method including:

a step of obtaining a semiconductor light emitting device substrate bythe production method according to any one of the aspects [1] to [14];and

a step of laminating a semiconductor functional layer including at leasta light emitting layer on a surface of the obtained semiconductor lightemitting device substrate where an uneven structure is formed.

[16] A semiconductor light emitting device substrate which is asemiconductor light emitting device substrate including an unevenstructure on one surface of the substrate,

wherein the aforementioned uneven structure includes numerous convexportions and a flat surface between the convex portions,

and also has a plurality of areas in which the central points of sevenadjacent convex portions are aligned continuously in a positionalrelationship so as to become six vertices and intersection point ofdiagonal lines of a regular hexagon, and

an area, shape and lattice orientation of the aforementioned pluralityof areas are random.

[17] The semiconductor light emitting device substrate according to theaspect [16],

wherein a most frequent pitch of the aforementioned uneven structure isnot greater than 5 μm, and

an aspect ratio of the aforementioned numerous convex portions is from0.5 to 1.0.

[18] The semiconductor light emitting device substrate according to theaspect [16],

wherein a most frequent pitch of the aforementioned uneven structure isnot greater than 1 μm, and

an aspect ratio of the aforementioned numerous convex portions is from0.5 to 1.0.

[19] The semiconductor light emitting device substrate according to theaspect [16],

wherein a most frequent pitch of the aforementioned uneven structure isfrom 200 nm to 700 nm, and

an aspect ratio of the aforementioned numerous convex portions is from0.5 to 1.0.

[20] The semiconductor light emitting device substrate according to anyone of the aspects [16] to [19],

further including a bridge portion connecting between the aforementionedconvex portions.

[21] The semiconductor light emitting device substrate according to anyone of the aspects [16] to [20],

wherein the aforementioned substrate is sapphire.

[22] A semiconductor light emitting device including:

the semiconductor light emitting device substrate described in any oneof the aspects [16] to [20]; and

a semiconductor functional layer laminated on the aforementionedsemiconductor light emitting device substrate,

wherein the aforementioned semiconductor functional layer includes atleast a light emitting layer.

[23] The semiconductor light emitting device according to the aspect[22] including a wavelength conversion layer for converting a wavelengthof light emitted from the aforementioned light emitting layer to a longwavelength side than a wavelength of the aforementioned light, in alight extraction side of the aforementioned semiconductor functionallayer.

[24] The semiconductor light emitting device according to the aspect[23],

wherein the aforementioned wavelength conversion layer includes a bluephosphor emitting fluorescence with a peak wavelength of 410 nm to 483nm, a green phosphor emitting fluorescence with a peak wavelength of 490nm to 556 nm, and a red phosphor emitting fluorescence with a peakwavelength of 585 nm to 770 nm.

[25] The semiconductor light emitting device according to the aspect[24],

wherein the aforementioned wavelength conversion layer includes a yellowphosphor emitting fluorescence with a peak wavelength of 570 nm to 578nm.

Advantageous Effects of Invention

According to some aspects of the present invention, it is possible toprovide a semiconductor light emitting device with which a sufficientlight extraction efficiency can be obtained and also the problems ofincreases in the color shift and in-plane anisotropy are prevented.

In addition, according to some aspects of the present invention, it ispossible to provide a semiconductor light emitting device substratecapable of forming a semiconductor layer with few crystal defects andsuitable for the manufacture of a semiconductor light emitting devicethat solves the above problems.

Further, some aspects of the present invention can provide a method ofmanufacturing a semiconductor light emitting device substrate which iscapable of manufacturing a semiconductor light emitting device substratethat solves the above problems, and is also capable of forming an unevenstructure with a pitch of not greater than 1 μm by a simple method atlow cost and in a short period of time.

Furthermore, some aspects of the present invention can provide a methodof manufacturing a semiconductor light emitting device capable ofmanufacturing a semiconductor light emitting device that solves theabove problems by using the method of manufacturing a semiconductorlight emitting device substrate that solves the above problems.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a semiconductorlight emitting device substrate of the present invention.

FIG. 2 is a plan view schematically showing a semiconductor lightemitting device substrate of the present invention.

FIG. 3A is an explanatory view of a method of manufacturing asemiconductor light emitting device substrate of the present invention,and shows a state after a particle arranging step.

FIG. 3B is an explanatory view of a method of manufacturing asemiconductor light emitting device substrate of the present invention,and shows a state after a particle etching step.

FIG. 3C is an explanatory view of a method of manufacturing asemiconductor light emitting device substrate of the present invention,and shows a state in the middle of a substrate etching step.

FIG. 3D is an explanatory view of a method of manufacturing asemiconductor light emitting device substrate of the present invention,and shows a state after the substrate etching step.

FIG. 4 is a plan view schematically showing particles arranged inamonolayer particle film forming step.

FIG. 5A is an explanatory view of a particle arranging step using an LBmethod, and shows a state before starting a transfer step.

FIG. 5B is an explanatory view of the particle arranging step using anLB method, and shows a state during the transfer step.

FIG. 6 is a partial perspective view showing an enlarged portion of asemiconductor light emitting device substrate according to an embodimentin a technique of the present disclosure.

FIG. 7 is a partial plan view showing an enlarged portion of a planarstructure of a semiconductor light emitting device substrate accordingto an embodiment.

FIG. 8 is a partial cross-sectional view showing a portion of across-sectional structure of a semiconductor light emitting devicesubstrate according to an embodiment, and is a partial cross-sectionalview as seen from a line 23-23 in FIG. 7.

FIG. 9 is a partial cross-sectional view showing a portion of across-sectional structure of a semiconductor light emitting devicesubstrate according to an embodiment, and is a partial cross-sectionalview as seen from a line 24-24 in FIG. 7.

FIG. 10 is a partial plan view showing a portion of a planar structureof a monolayer particle film formed in a step of forming a monolayerparticle film in a method of manufacturing a semiconductor lightemitting device substrate according to an embodiment.

FIG. 11 is a partial plan view showing a portion of a planar structureof a monolayer particle film etched in a step of etching a monolayerparticle film in a method of manufacturing a semiconductor lightemitting device substrate according to an embodiment.

FIG. 12 is a partial plan view showing a portion of a planar structureof a light emitting structure forming surface etched in a step ofetching a light emitting structure forming surface in a method ofmanufacturing a semiconductor light emitting device substrate accordingto an embodiment.

FIG. 13 is a partial cross-sectional view schematically showing aportion of a cross-sectional structure of a semiconductor light emittingdevice according to an embodiment.

FIG. 14 is a partial perspective view showing an enlarged portion of across-sectional structure of a semiconductor light emitting devicesubstrate in a semiconductor light emitting device substrate of amodified example in a technique of the present disclosure, and one onthe left side is a view corresponding to FIG. 8 which will be describedin an embodiment, while one on the right side is a view corresponding toFIG. 9 which will be described in an embodiment.

FIG. 15 is a partial perspective view showing an enlarged portion of across-sectional structure of a semiconductor light emitting devicesubstrate in a semiconductor light emitting device substrate of amodified example in a technique of the present disclosure, and one onthe left side is a view corresponding to FIG. 8 which will be describedin an embodiment, while one on the right side is a view corresponding toFIG. 9 which will be described in an embodiment.

DESCRIPTION OF EMBODIMENTS

[First Embodiment]

<Semiconductor Light Emitting Device Substrate>

A semiconductor light emitting device substrate 11 according to anembodiment of the present invention will be described using FIGS. 1 and2. As shown in FIG. 1, the semiconductor light emitting device substrate11 has an uneven structure on one surface of the substrate.

The uneven structure of the substrate surface has a number of convexportions c1 l to c1 n. In addition, present between the convex portionsare flat surfaces f1 l to f1 n.

t1 l to t1 n in FIG. 1 are central points of the convex portions c1 l toc1 n. Based on the measurement results of an atomic force microscope(AFM), a plurality of contour lines are drawn for every 20 nm for theconvex portions in parallel to the reference plane to determine thecenter of gravity (the point determined by the x and y coordinates) ofeach contour line. The average position of each of these centers ofgravity (the position point determined by the average of x coordinatesand the average of y coordinates) is the central point of the convexportion.

m1 l to m1 n in FIG. 1 are midpoints of the adjacent central pointdetermined by AFM. In addition, the flat surfaces f1 l to f1 n areregions in which the inclination of a linear line connecting the surfaceheight at the midpoint within that region and the surface height of anypoint within that region, with respect to the reference plane of theAFM, is equal to or less than ±10°, based on the AFM measurements.

The periphery of the flat surfaces f1 l to f1 n is preferably presentwithin the distance of 2 nm to 300 nm, and more preferably within thedistance of 5 nm to 100 nm, from the middle points m1 to mn, when a mostfrequent pitch P of the uneven structure is not greater than 1 μm. Whenthe most frequent pitch P of the uneven structure exceeds 1 μm, theperiphery of the flat surfaces f1 l to f1 n is preferably present withinthe distance of 100 nm to 3000 nm, and more preferably within thedistance of 200 nm to 2,000 nm, from the middle points m1 l to m1 n.

If the distance between the periphery of the flat surfaces and themidpoints is equal to or more than the preferred lower limit, sufficientarea of the flat surface is secured, and it would be easy to epitaxiallygrow a semiconductor layer stably on the substrate. In addition, if thedistance between the periphery of the flat surfaces and the midpoints isequal to or less than the preferred upper limit, it would be easy toform convex portions with sufficient density and to obtain an improvedeffect of the light extraction efficiency.

Further, convex portions c1 l to c1 n are formed so that the flatsurfaces f1 l to f1 n are arranged as follows. Convex portions c1 l toc1 n are formed so that the length of the flat surfaces f1 l to f1 nwhen viewed in a cross section perpendicular to the substrate, that is,the cross section shown in FIG. 1, through the apex of the convexportions c1 l to c1 n is preferably from 5% to 40%, and more preferablyfrom 15% to 25%, with respect to a straight line connecting the apexesof the two adjacent convex portions of the convex portions c1 l to c1 n.

Examples of the shape of the convex portion include a cone, a truncatedcone, a bamboo shoot-like shape in which the slope of a cone is bulgingoutward, a semi-spherical shape, and a shape in which the slope of atruncated cone is bulging outside (a shape prepared by cutting the topof a bamboo shoot-like or semi-spherical shape).

The most frequent pitch P of the uneven structure is preferably from 100nm to 5 μm, more preferably from 100 nm to 1 μm, still more preferablyin the range of 200 nm to 700 nm, and particularly preferably in therange of 300 nm to 600 nm. If the most frequent pitch P is within thepreferred range, it is easy to prevent the total reflection of light. Inparticular, if the most frequent pitch P is equal to or less than 1 μm,it is possible to increase the light extraction efficiency of the blueto violet light more effectively. Therefore, it is suitable as an unevenstructure of a substrate used for a semiconductor light emitting devicehaving an emission wavelength of blue to ultraviolet region by carryingout the deposition of GaN, InGaN or the like.

More specifically, the most frequent pitch P is determined in thefollowing manner.

First, in a region that is randomly selected in an uneven surface, bydefining a plane parallel to the substrate surface in a square areahaving one side 30 to 40 times as large as the most frequent pitch P asan AFM reference surface, an AFM image is obtained for the square area.For example, if the most frequent pitch is about 300 nm, an image of anarea from 9 μm×9 μm to 12 μm×12 μm is obtained. Then, the image isseparated by the waveform through Fourier transform to obtain an FFTimage (Fast Fourier transform image). Next, the distance from thezero-order peak to the primary peak in the profile of the FFT image isdetermined. A reciprocal of the distance thus determined is the mostfrequent pitch P in this region. Such a process is conducted in asimilar manner for regions having the same area of a total of 25 or morelocations that are chosen randomly to determine the most frequent pitchin each region. The average value of the most frequent pitches P₁ to P₂₅in the regions of 25 or more locations obtained in this manner is themost frequent pitch P. It should be noted that at this time, it ispreferable that the regions that are separated by at least 1 mm fromeach other are selected, and it is more preferable that those that areseparated by 5 mm to 1 cm are selected.

A most frequent height H of the convex portion is preferably adjustedbetween 50 nm and 5 μm. In particular, when the most frequent pitch P isnot greater than 1 μm, the most frequent height H of the convex portionis preferably equal to or more than 50 nm and equal to or less than 1μm, and more preferably equal to or more than 100 nm and equal to orless than 700 nm.

If the most frequent height H is within the preferred range, depositiondefects of the nitride compounds to be deposited later are reduced, and,moreover, it is possible to prevent the total reflection of light and toimprove the light extraction efficiency.

More specifically, the most frequent height H of the convex portion isdetermined in the following manner.

First, a cross-section that passes through the apex of the convexportions c1 l to c1 n along a line having a length of 1 mm in anarbitrary direction and position and is perpendicular to the substrate,that is, the cross-section as in FIG. 1 is obtained from the AFM image.An arbitrary portion containing at least 30 convex portions of the crosssection is extracted, and for each convex portion contained therein, adifference between the height of the vertex and the height of the lowestposition in a flat portion between the aforementioned convex portion andan adjacent convex portion is determined. The resulting values arerounded with a valid digit number of two digits and defined as a heightfor each convex portion, and the most frequent value thereof is definedas the most frequent height H.

As shown in FIG. 2, the semiconductor light emitting device substrate 11includes a plurality of areas C₁₁ to C_(1n).

The areas C1 l to C1 n are areas in which the central points of sevenadjacent convex portions are aligned continuously in a positionalrelationship so as to become six vertices and intersection point ofdiagonal lines of a regular hexagon. It should be noted that in FIG. 2,the position of the central point of each convex section is shown, forconvenience, by a circle u1 centered on the central point. As shown inFIG. 1, the circle u1 corresponds not only to the convex portion butalso to a region including a flat surface in the periphery thereof.

More specifically, in the present embodiment, a positional relationshipso that the central points of the seven adjacent convex portions are tobecome six vertices and intersection point of diagonal lines of aregular hexagon refers to a relationship that satisfies the followingconditions.

First, from one central point t11, a line segment L1 having an equallength as the most frequent pitch P in the direction of the adjacentcentral point t12 is drawn. Then, from the central point t11, withrespect to the line segment L1 line segments L2 to L6 having an equallength as the most frequent pitch P are drawn in each direction of 60°,120°, 180°, 240° and 300°. If the six central points adjacent to thecentral point t11 are each within the range of 15% or less of the mostfrequent pitch P from each of the end points of the line segments L1 toL6 on the opposite side of the central point t11, these seven centralpoints are in a positional relationship so as to become six vertices andintersection point of diagonal lines of a regular hexagon.

A most frequent area Q of the areas C₁₁ to C_(1n) (most frequent valueof the area size) is preferably within the following range.

When the most frequent pitch P is less than 500 nm, the most frequentarea Q within the AFM image measuring range of 10 mm×10 mm is preferablyfrom 0.026 μm² to 6.5 mm².

When the most frequent pitch P is equal to or greater than 500 nm andless than 1 μm, the most frequent area Q within the AFM image measuringrange of 10 mm×10 mm is preferably from 0.65 μm² to 26 mm².

When the most frequent pitch P is equal to or greater than 1 μm, themost frequent area Q within the AFM image measuring range of 50 mm×50 mmis preferably from 2.6 μm² to 650 mm².

If the most frequent area Q is within the preferred range, it is easy toprevent the problems of increase in the color shift and in-planeanisotropy of light.

In addition, as shown in FIG. 2, the areas C₁₁ to C_(1n) have randomareas, shapes and lattice orientations. It should be noted that thelattice orientation of areas C₁₁ to C_(1n) herein refers to thedirection of a primitive translation vector (two vectors are present inthe case of triangular lattice) obtained by connecting the vertices ofthe adjacent convex portions in the same area when viewed from the uppersurface of the substrate.

More specifically, the degree of area randomness preferably satisfiesthe following conditions.

First, an ellipse having the largest area in which boundaries of onearea are circumscribed is drawn and the ellipse is represented by thefollowing formula (α).X ² /a ² +Y ² /b ²1  (α)

When the most frequent pitch P is less than 500 nm, the standarddeviation of πab in the AFM image measuring range of 10 mm×10 mm ispreferably at least 0.08 μm².

When the most frequent pitch P is equal to or greater than 500 nm andless than 1 μm, the standard deviation of πab in the AFM image measuringrange of 10 mm×10 mm is preferably at least 1.95 μm².

When the most frequent pitch P is equal to or greater than 1 μm, thestandard deviation of πab in the AFM image measurement range of 50 mm×50mm is preferably at least 8.58 μm².

If the standard deviation of πab is within the preferred range, theeffect of averaging of the diffracted light is excellent.

In addition, more specifically, the degree of the shape randomness ofthe areas C₁₁ to C_(1n) is preferably such that the standard deviationof a/b (ratio of a and b) in the above formula (α) is 0.1 or more.

Further, more specifically, the randomness of the lattice orientation ofthe areas C¹¹ to C_(1n) preferably satisfies the following conditions.

First, a straight line K0 connecting the central points of the twoarbitrary adjacent convex portions in an arbitrary area (I) is drawn.Next, one area (II) adjacent to the area (I) is selected, six straightlines K1 to K6 connecting an arbitrary convex portion in the area (II)and the central points of the six convex portions adjacent to thearbitrary convex portion are drawn. If all of straight lines K1 to K6are different by an angle of 3 degrees or more, with respect to thestraight line K0, it is defined that the lattice orientations of thearea (I) and the area (II) are different.

Among the areas adjacent to the area (I), it is preferable that two ormore areas having a different lattice orientation from the latticeorientation of the area (I) be present, more preferably three or moresuch areas be present, and still more preferably five or more such areasbe present.

The uneven structure of the semiconductor light emitting devicesubstrate 11 has an arrangement like a polycrystalline structure inwhich the lattice orientation is aligned in each of the areas C₁₁ toC_(1n), but is not aligned macroscopically. Macroscopic randomness oflattice orientations can be evaluated by the ratio of the maximum valueand the minimum value of the FFT (Fast Fourier Transform) fundamentalwave. The ratio of the maximum value and the minimum value of the FFTfundamental wave is determined by obtaining an AFM image and obtainingthe two-dimensional Fourier transform image thereof, and then drawing acircle separated from the origin by the wave number of the fundamentalwave, extracting a point where the amplitude is the greatest and a pointwhere the amplitude is the smallest on the circumference, and derivingas the ratio of the amplitudes. A method of obtaining the AFM image inthis case is the same as the method of obtaining the AFM image indetermining the most frequent pitch P.

An uneven structure in which the ratio of the maximum value and theminimum value of the FFT fundamental wave is large has an alignedlattice orientation and can be said to have a structural configurationwith high single crystallinity when regarding the uneven structure as atwo-dimensional crystal. Conversely, uneven structure in which the ratioof the maximum value and the minimum value of the FFT fundamental waveis small has a non-aligned lattice orientation and can be said to havean arrangement like a polycrystalline structure when regarding theuneven structure as a two-dimensional crystal.

When the uneven structure of the semiconductor light emitting devicesubstrate 11 has a ratio of the maximum value and the minimum value ofthe FFT fundamental wave within the above preferred range, thediffracted light is not radiated in a particular in-plane direction, andthe diffracted light is radiated uniformly. Therefore, there are notcases where the radiation intensity of the semiconductor light emittingdevice is different depending on the viewing angle. In other words, itis possible to obtain a semiconductor light emitting device with lowin-plane radiation anisotropy.

In addition, the occurrence of color shift in the semiconductor lightemitting device can also be prevented. Color shift is a phenomenon inwhich color is different depending on the viewing angle. For example, inthose cases where the light wavelength is converted by a phosphor andthen the light is once again diffracted in the device due to the unevenstructure of the semiconductor light emitting device substrate 11 (abottom emission type white LED or the like that is provided with areflective electrode on the upper surface and converts the ultravioletlight to white light by three primary phosphors), the diffracted lightoverlaps the original spectrum, which results in the intensification ofa particular wavelength.

If the uneven structure has a ratio of the maximum value and the minimumvalue of the FFT fundamental wave within the above preferred range, itis possible to avoid deviation in the emission angle of the diffractedlight, and therefore it is possible to suppress the color shift.

The uneven structure of the semiconductor light emitting devicesubstrate 11 has a moderate level of randomness. Therefore, it ispossible to prevent the problem of an increase in the color shift andin-plane anisotropy by achieving sufficient light extraction efficiencyand also by averaging the diffracted light. In addition, since the spacebetween the convex portions is a flat surface, it is possible to grow asemiconductor layer in a stable manner.

<Method of Manufacturing a Semiconductor Light Emitting DeviceSubstrate>

A method of manufacturing a semiconductor light emitting devicesubstrate according to the present embodiment includes: a particlearranging step for arranging a plurality of particles on a substrate; aparticle etching step for dry etching the aforementioned plurality ofparticles arranged to provide a void between the particles in acondition by which the aforementioned particles are etched while theaforementioned substrate is not etched substantially; and a substrateetching step for dry etching the aforementioned substrate by using theplurality of particles after the aforementioned particle etching step asan etching mask, thereby forming an uneven structure on one side of theaforementioned substrate.

Hereinafter, after describing a substrate (substrate before processing)used in the method of manufacturing a semiconductor light emittingdevice substrate of the present embodiment, each step will besequentially described along FIG. 3A to FIG. 3D. It should be noted thatin FIG. 3A to FIG. 3D, for convenience of explanation, irregularitiesformed on particles M and substrate S are extremely enlarged.

[Substrate]

As a material for the substrate, it is possible to use a plate materialmade of a material, such as sapphire, SiC, Si, MgAl₂O₄, LiTaO₃, LiNbO₃,ZrB₂, GaAs, GaP, GaN, AlN, AlGaN, InP, InSn, InAlGaN or CrB₂. Amongthem, in view of mechanical stability, thermal stability, opticalstability, chemical stability, and also optical transparency, sapphireis preferred.

The method of manufacturing a semiconductor light emitting devicesubstrate of the present embodiment is capable of accurately forming adesired uneven structure, not only on a substrate with high flatness,but also on a substrate with low flatness. This is because it ispossible to accurately form a uniform monolayer particle film mask in amonolayer even on a substrate with low flatness, since a monolayerparticle film to be used in the present embodiment is formed, even ifthere are irregularities to some extent on the substrate, by followingthem.

More specifically, even when a substrate is used, in which the absolutedifference (TTV) between the maximum thickness and the minimum thicknessas defined in ASTM F657 is from 5 μm to 30 μm, the difference (WARP)between the maximum value and the minimum value of the deviation fromthe reference plane as defined in ASTM F1390 is from 10 μm to 50 μm, andthe absolute value (|BOW|) of the distance from the reference plane atthe center of the substrate as defined by ASTM F534.3.1.2 is from 10 μmto 50 μm, it is possible to obtain a semiconductor light emitting devicesubstrate satisfying the following formula (3).H′=(2.5±0.5)P^(−0.4±0.1)±1.5  (3)

Here, H′ is a coefficient of variation for the height of the unevenstructure, P is the most frequent pitch (μm) of the uneven structureformed on a substrate by the present embodiment.

The coefficient of variation H′ is generally determined in the followingmanner. First, the most frequent height H is determined as describedabove, and after determining the average value μ=ΣH/n(ΣH: total numberof data, n=the number of data) and standard deviation σ=((Σ(H−μ)^2)/n)^(½), the coefficient of variation H′=σ/μ×100 is thendetermined. In addition, the way of determining the most frequent pitchP is as described above. For the present embodiment, after obtaining thecoefficient of variation for each pitch, an empirical formula (3) wasobtained by taking the coefficient of variation on the vertical axis andthe pitch on the horizontal axis.

If the uneven structure of the semiconductor light emitting devicesubstrate satisfies the formula (3), deposition defects of the nitridecompound to be deposited subsequently can be reduced, and it becomespossible to further prevent the total reflection of light to improve thelight extraction efficiency. As the condition for reducing thedeposition defects, the coefficient of variation H′ is preferably 10% orless, more preferably 5% or less, and still more preferably 3% or less.In the present embodiment, it has been found that the formula (3) alwaysholds for the entire surface of the substrate, even when a substratewith low flatness within the range of TTV of 5 μm to 30 μm, WARP of 10μm to 50 μm, and |BOW| of 10 μm to 50 μm. On the other hand, accordingto the semiconductor light emitting device substrate prepared byphotolithography which is a conventional method, although depending onthe thickness of the photoresist used as a mask, the entire surface ofthe substrate, it is difficult to set the coefficient of variation H′ to10% or less within the abovementioned ranges for the TTV, WARP and|BOW|.

[Particle Arranging Step]

In the particle arranging step, as shown in FIG. 3A, a plurality ofparticles M₁ are arranged in a single layer on a flat surface X which isone surface of a substrate S₁. In other words, a monolayer particle filmof particles M₁ is formed.

Although the particles M₁ are preferably inorganic particles, organicpolymer materials and the like can also be used, depending on theconditions. If inorganic particles are used, they can be easily etchedin the particle etching step under a condition in which a substrate M isnot substantially etched.

As the inorganic particles, for example, it is possible to use particlesmade of oxides, nitrides, carbides, borides, sulfides, selenides andcompounds of metals and the like, metal particles and the like. As theorganic particles, thermoplastic resins, such as polystyrene and PMMA,and thermosetting resins, such as phenolic resins and epoxy resins, canbe used.

Examples of those that can be used as an oxide include silica, alumina,zirconia, titania, ceria, zinc oxide, tin oxide and yttrium aluminumgarnet (YAG), and, furthermore, those in which these constituentelements are partially substituted with another element can also beused.

Examples of those that can be used as a nitride include silicon nitride,aluminum nitride and boron nitride, and, furthermore, those in whichthese constituent elements are partially substituted with anotherelement can also be used.

For example, compounds such as sialon composed of silicon, aluminum,oxygen and nitrogen can also be used.

Examples of those that can be used as a carbide include SiC, boroncarbide, diamond, graphite and fullerenes, and, furthermore, those inwhich these constituent elements are partially substituted with anotherelement can also be used.

Examples of those that can be used as a boride include ZrB₂ and CrB₂,and, furthermore, those in which these constituent elements arepartially substituted with another element can also be used.

Examples of those that can be used as a sulfide include zinc sulfide,calcium sulfide, cadmium sulfide and strontium sulfide, and,furthermore, those in which these constituent elements are partiallysubstituted with another element can also be used.

Examples of those that can be used as a selenide include zinc selenideand cadmium selenide, and, furthermore, those in which these constituentelements are partially substituted with another element can also beused.

As those that can be used as a metal, particles composed of one or moremetals selected from the group consisting of Si, Ni, W, Ta, Cr, Ti, Mg,Ca, Al, Au, Ag and Zn can be used.

The inorganic particles described above can be used not only eachindependently as particles M₁, but also as particles M by mixing theseinorganic particles.

In addition, coated particles like those obtained by coating inorganicparticles composed of a nitride with an oxide can also be used as theparticles M₁. Furthermore, it is possible to use phosphor particlesobtained by introducing an activator such as cerium and europium in theinorganic particles described above as the particles M₁.

In addition, the particles M₁ may be a mixture of two or more types ofparticles composed of different materials from each other. Further, theparticles M₁ may be a laminate composed of different materials, and, forexample, may be particles obtained by coating inorganic particlescomposed of an inorganic nitride with an inorganic oxide.

Among the compounds constituting the inorganic particles describedabove, oxides are preferred in terms of shape stability, among whichsilica is more preferred.

In the particle arranging step, a plurality of particles M₁ are arrangedin a single layer on the substrate S₁ so that a deviation D(%) of thearrangement defined by the following formula (1) becomes 15% or less:D[%]=|B−A|×100/A  (1)

Note that in the formula (1), A denotes an average particle diameter ofthe particles M₁, B denotes the most frequent pitch between theparticles M₁. Moreover, |B−A| denotes an absolute value of thedifference between A and B.

The deviation D is preferably at least 0.5% and not greater than 15%,more preferably at least 1.0 and not greater than 10%, and still morepreferably from 1.0% to 3.0%.

Here, the average particle diameter A of particles M₁ refers to anaverage primary particle diameter of the particles M₁ constituting amonolayer particle film, and can be determined by a conventional methodfrom a peak obtained by fitting a particle size distribution determinedby a particle dynamic light scattering method to a Gaussian curve.

On the other hand, the pitch between the particles M refers to adistance between vertexes of the two adjacent particles M₁ in a sheetplane direction, and the most frequent pitch B between the particles M₁is the most frequent value thereof. It should be noted that if theparticles M₁ have a spherical shape and come into contact with eachother without a gap, the distance between the vertexes of adjacentparticles M₁ is equal to the distance between the centers of adjacentparticles M₁.

Since the pitch of the uneven structure of the semiconductor lightemitting device substrate according to the present embodiment reflectsthe pitch between the particles M₁, the preferred most frequent pitch Bbetween the particles M₁ is the same as the preferred most frequentpitch P in the uneven structure of the semiconductor light emittingdevice substrate according to the present embodiment. That is, the mostfrequent pitch B between the particles M₁ is preferably from 100 nm to 5μm, more preferably from 100 nm to 1 μm, still more preferably in therange of 200 nm to 700 nm, and particularly preferably in the range of300 nm to 600 nm.

More specifically, the most frequent pitch B between the particles M₁ isobtained in the following manner.

First, in a randomly selected area in a monolayer particle film, an AFMimage is obtained for a square region that has one side 30 times to 40times as large as the most frequent pitch B between the particles M₁ andis in parallel to a sheet plane. For example, in the case of a monolayerparticle film using a particle M₁ having a particle size of 300 nm, animage of an area of 9 μm×9 μm to 12 μm×12 μm is obtained. Then, theimage is separated into waveforms through Fourier transformation toobtain an FFT image (Fast Fourier transform image). Next, a distancefrom the zero-order peak to the primary peak in the profile of the FFTimage is determined. The reciprocal of the distance thus determined isthe most frequent pitch B₁ in this region. Such a process is carried outfor regions having the same area in a similar manner over a total of 25regions or more selected at random to determine the most frequentpitches B₁ to B₂₅ in each region. An average value of the most frequentpitches B₁ to B₂₅ in 25 or more regions thus obtained is the mostfrequent pitch B in the formula (1). It should be noted that in thiscase, the regions are preferably selected by being separated from eachother by at least 1 mm, and more preferably selected by being separatedby 5 mm to 1 cm.

In addition, at this time, from the area of the primary peak in theprofile of the FFT images, for each image, it is also possible toevaluate the variation in the pitches between the particles M therein.

A deviation D of this arrangement is an indicator indicating the degreeof the closest packing of particles M₁. That is, a small deviation D ofthe arrangement of the particles means that the degree of the closestpacking high, intervals between the particles are controlled, and theaccuracy of the arrangement is high.

Since the deviation D(%) of the arrangement is set to 15% or less, thevariation coefficient (a value obtained by dividing the standarddeviation by the average value) of the particle size of the particles M₁is preferably 20% or less, more preferably 10% or less, and still morepreferably 5% or less.

As described later, the pitch having an uneven structure provided on thesubstrate S₁ according to the present embodiment (the pitch of thecentral point of the convex portion) is equivalent to the most frequentpitch B between the particles M₁. Since the pitch of an uneven structurebecomes substantially equivalent to an average particle diameter A ofthe particles M₁ if the deviation D(%) of the arrangement is small, byappropriately selecting the average particle diameter A of the particlesM₁, it is possible to form the desired uneven structure of the pitchwith high accuracy.

In addition, if a most frequent height H with respect to a most frequentsize R of the bottom surface of the convex portions c1 l to c1 n isdefined as the aspect ratio, the aspect ratios of the convex portions c1l to c1 n are from 0.5 to 1.0. The bottom surface of the convex portionc1 l to c1 n refers to a surface to be surrounded by the boundarybetween the flat surface f1 n and the convex portion c1 n. The sizes R1l to R1 n of the bottom surface of the convex portions c1 l to c1 n, ina straight line passing through the central point t1 n, the distancebetween two points crossing the boundary between the flat surface f1 nand the convex portion c1 n. The most frequent size R can be calculatedin the following manner.

First, from an AFM image, an arbitrary portion that can include 30 ormore convex portions c1 n is extracted, the dimensions of the bottomsurface of the convex portion are determined for each convex portion c1n included therein by the above method, the obtained values are roundedby the number of significant figures of two digits, the bottom diametersof each convex portion c1 n are denoted as R1 l to R1 n, and the mostfrequent value thereof is defined as the most frequent size R.

By setting the aspect ratio of the convex portions c1 l to c1 n from 0.5to 1.0, light is hardly trapped between the convex portions c1 l to c1n, thereby improving the light extraction efficiency.

[Particle Arranging Step by LB Method]

The particle arranging step is preferably carried out by a methodutilizing the concept of the so-called LB method (Langmuir-Blodgettmethod).

More specifically, it is preferable to perform the particle arrangingstep by a method including a dropping step for dropwise adding adispersion in which particles are dispersed in a solvent having asmaller specific gravity than water to the liquid surface of the waterin a water tank, a monolayer particle film forming step for forming amonolayer particle film composed of particles by vaporizing the solvent,and a transfer step for transferring the monolayer particle film onto asubstrate.

This method combines the accuracy of conversion into a monolayer, easeof operation, handling of a larger area size, reproducibility and thelike. For example, it is highly superior compared to a liquid thin filmmethod described in Nature, Vol. 361, 7 Jan. 26, 1993 or the like andthe so-called particle adsorption method described in JapaneseUnexamined Patent Application, First Publication No. Sho 58-120255 orthe like, and can also handle the industrial production level.

The particle arranging step the by LB method will be described below inmore detail.

(Dropping Step and Monolayer Particle Film Forming Step)

First, a dispersion is prepared by adding particles M₁ in a solventhaving a specific gravity smaller than that of water. On the other hand,a water tank (trough) is prepared, into which water (hereinafter, alsoreferred to as underlying water in some cases) is poured in order toexpand the particles M₁ on the liquid surface thereof.

It is preferable that the surface of the particles M₁ is hydrophobic. Inaddition, as a solvent, it is preferable to select a hydrophobicsolvent. By combining the hydrophobic particles M₁ and solvent and theunderlying water, as described later, the self-organization of particlesM₁ is allowed to proceed, thereby forming a monolayer particle filmwhich is closely packed two-dimensionally.

It is also important that the solvent be highly volatile. Examples ofthe solvent that is highly volatile and hydrophobic include volatileorganic solvents composed of one or more of chloroform, methanol,ethanol, isopropanol, acetone, methyl ethyl ketone, ethyl ethyl ketone,toluene, hexane, cyclohexane, ethyl acetate and butyl acetate.

In those cases where the particles M₁ are inorganic particles, since thesurface thereof is usually hydrophilic, it is preferable to make themhydrophobic with a hydrophobizing agent for use. As the hydrophobizingagent, a surface active agent, a metal alkoxysilane or the like can beused.

Hydrophobization of the particles M₁ can be carried out using the samesurface active agent, metal alkoxysilane or the like as thehydrophobizing agent described in Japanese Unexamined PatentApplication, First Publication No. 2009-162831 and by the same methoddescribed therein.

In addition, in order to further enhance the accuracy of the monolayerparticle film to be formed, it is preferable to subject the dispersionliquid before adding dropwise to the liquid surface to microfiltrationusing a membrane filter or the like to remove the aggregated particles(secondary particles composed of multiple primary particles) present inthe dispersion liquid. If the microfiltration is carried out in advancein this manner, portions where two or more layers are partially formedor defective portions where no particles are present are hardlygenerated, and a monolayer particle film with high accuracy can beeasily obtained.

In the transfer step to be described later in more detail, if an LBtrough device equipped with a surface pressure sensor for measuring thesurface pressure of a monolayer particle film and a movable barrier forcompressing the monolayer particle film in the liquid surface directionis used, it is possible to detect the defective portions of themonolayer particle film formed to some extent based on the difference inthe surface pressure.

However, defective portions having a size of about several micrometersto several tens of micrometers are less likely to be detected as adifference in the surface pressure. If the microfiltration is carriedout in advance, defects having a size of about several micrometers toabout several tens of micrometers become less likely to occur, and itbecomes easy to obtain a monolayer particle film with high accuracy.

The dispersion liquid described above is added dropwise to the liquidsurface of the underlying water (dropping step). Then, the solventserving as a dispersion medium is volatilized, and at the same time, theparticles M₁ are expanded in a monolayer on the liquid surface of theunderlying water, thereby making it possible to forma monolayer particlefilm which is closely packed two-dimensionally (monolayer particle filmforming step).

It is preferable to set the particle concentration of the dispersionliquid to be added dropwise to the underlying water from 1% by mass to10% by mass. In addition, it is preferable to set the dropping rate from0.001 ml/sec to 0.01 ml/sec. If the concentration and addition amount ofthe particles M₁ in the dispersion liquid are within such ranges,tendencies such as partial aggregation of the particles like a clusterto form two or more layers, generation of a defective portion where noparticles are present and widening of the pitch between the particlesare suppressed. For this reason, a monolayer particle film in which eachparticle is closely packed two-dimensionally with high accuracy can beobtained more easily.

In the monolayer particle film forming step, a monolayer particle filmis formed by the self-organization of particles M₁. The principle isthat when the particles are assembled, the surface tension caused due tothe dispersion medium present between the particles acts, as a result ofwhich the particles M₁ are not present randomly from each other butautomatically form a two-dimensionally close-packed structure. Suchclose packing by the surface tension can also be described, in anotherexpression, as an arrangement by capillary force in a transversedirection.

In particular, for example, like colloidal silica, when three particlesM₁ having a spherical shape with highly uniform particle size aregathered and brought into contact in a state of floating on the watersurface, surface tension acts so as to minimize the total length of thewaterline of the particle groups. As a result, as shown in FIG. 4, thethree particles M₁ are stabilized in an arrangement which is based on anequilateral triangle indicated as T₁ in the drawing.

The monolayer particle film forming step is preferably carried out inultrasonic irradiating conditions. When the solvent of the dispersionliquid is volatilized while applying ultrasonic waves from theunderlying water toward the water surface, closest packing of particlesM is promoted, and a monolayer particle film in which each particle M₁is close-packed two-dimensionally with higher accuracy is obtained. Atthis time, the output of the ultrasonic wave is preferably from 1 W to1,200 W and more preferably from 50 W to 600 W.

In addition, although there is no particular limitation on the frequencyof ultrasonic waves, for example, it is preferably from 28 kHz to 5 MHzand more preferably from 700 kHz to 2 MHz. If the frequency is too high,since the energy absorption of water molecules begins and a phenomenonin which water vapor or water droplets rise out of the water surfaceoccurs, it is undesirable. On the other hand, if the frequency is toolow, cavitation radius in the underlying water increases, and waterbubbles are generated in the water and emerge towards the water surface.When such bubbles accumulate under a monolayer particle film, it isdisadvantageous since the flatness of the water surface is lost.

A stationary wave is generated on the water surface by ultrasonicirradiation. If the output is too high at any given frequency or thewave height of the water surface is too high depending on the tuningcondition of the ultrasonic vibrator and transmitter, a caution isrequired since a monolayer particle film is destroyed by water waves.

When the frequency and the output of the ultrasonic waves are setappropriately by keeping the above in mind, it is possible to facilitatethe close packing of particles effectively without destroying themonolayer particle film which is being formed. In order to performeffective ultrasonic irradiation, it is preferable to use the naturalfrequency calculated from the size of the particles as a rough guide.However, since the natural frequency becomes extremely high as theparticles become small with a particle size of for example, 100 nm orless, it becomes difficult to give an ultrasonic vibration as thecalculation result suggests. In such a case, if a calculation is carriedout based on the assumption that the natural frequency corresponding tothe mass of the particle from dimers up to about 20-mers is given, it ispossible to reduce the frequency required to a practical range. Evenwhen an ultrasonic vibration corresponding to the natural frequency ofthe aggregates of particles is applied, the effect of improving the fillfactor of the particle is expressed. Irradiation time of the ultrasonicwaves may be of any length as long as it is sufficient to completerearrangement of the particles, and the time required varies dependingon the particle size, ultrasonic frequency, water temperature and thelike. However, under normal preparation conditions, it is preferablycarried out from 10 seconds to 60 minutes and more preferably from 3minutes to 30 minutes.

Other advantages obtained by the ultrasonic irradiation include, inaddition to closest packing of the particles (hexagonal close-packing ofrandom arrangements), the effect of destroying a soft aggregate ofparticles which is likely to occur during preparation of the dispersionliquid of nanoparticles, and the effect of repairing point defects, linedefects, crystal transition or the like that has once occurred, to someextent.

(Transfer Step)

A monolayer particle film formed on the liquid surface by the monolayerparticle film forming step is then transferred onto a substrate S₁ whilein a monolayer state (transfer step).

There is no particular limitation on the specific method fortransferring a monolayer particle film on the substrate S₁, and examplesinclude a method in which the hydrophobic substrate S₁ is lowered fromabove and brought into contact with the monolayer particle film whilekeeping a state of being substantially parallel to the monolayerparticle film, and the monolayer particle film is transferred onto andtaken up by the substrate S₁ due to the affinity between the monolayerparticle film and the substrate that are both hydrophobic; and a methodin which the substrate S₁ is placed in advance in the underlying waterin the water tank in a substantially horizontal direction prior to theformation of the monolayer particle film, and the monolayer particlefilm is formed on the liquid surface and then the liquid surface isgradually lowered, thereby transferring the monolayer particle film tothe substrate S₁.

Although a monolayer particle film can be transferred onto the substrateS₁ by the above methods without using a special device, it is preferableto adopt the so-called LB trough method (see Journal of Materials andChemistry, Vol. 11, 3333 (2001), Journal of Materials and Chemistry,Vol. 12, 3268 (2002), and the like) in the steps thereafter, in view ofeasy transfer onto the substrate S₁, even when the monolayer particlefilm has a larger surface area, while maintaining the two-dimensionalclosest packing state thereof.

FIGS. 5A and 5B schematically shows the outline of the LB trough method.It should be noted that in FIGS. 5A and 5B, for the convenience ofexplanation, particles M are extremely enlarged.

In this method, the substrate S₁ is previously immersed in advance inunderlying water W₁ in a water tank V₁ in a substantially verticaldirection, and the dropping step and the monolayer particle film formingstep described above are carried out in that state to form a monolayerparticle film F₁ (FIG. 5A). Then, after the monolayer particle filmforming step, by pulling the substrate S₁ upward while maintaining thesubstantially vertical direction, the monolayer particle film F can betransferred onto the substrate S₁ (FIG. 5B).

It should be noted that in this drawing, although a state in which themonolayer particle film F₁ is transferred onto both surfaces of thesubstrate S₁ is shown, since an uneven structure may be formed on onlyone surface of the substrate S₁, the monolayer particle film F₁ may betransferred only onto a flat surface X₁ of the substrate S₁. Byshielding a surface (back surface) opposite to the flat surface X₁ ofthe substrate S₁ with a thick plate, if the monolayer particle film F₁is transferred only to the flat surface X₁ in a state of preventing thegoing around of particles M₁ to the back surface from the flat surfaceX₁ side, it is preferable since the monolayer particle film F₁ can betransferred more precisely. However, there is no problem even if thetransfer takes place on both surfaces.

Here, since the monolayer particle film F₁ is formed already in thestate of a monolayer on the liquid surface by the monolayer particlefilm forming step, even if the temperature conditions (temperature ofthe underlying water), the pulling speed of the substrate S₁ or the likein the transfer step is somewhat varied, there is no possibility of themonolayer particle film F₁ being collapsed, turned into a multi-layer orthe like in the transfer step. It should be noted that the temperatureof the underlying water is usually dependent on the ambient temperaturethat varies due to the season and weather, and is approximately from 10°C. to about 30° C.

In addition, at this time, as the water tank V₁, it is preferable to usean LB trough device equipped with a surface pressure sensor not shownfor measuring the surface pressure of the monolayer particle film F₁based on the principle, such as a Wilhelmy plate, and a movable barriernot shown for compressing the monolayer particle film F₁ in thedirection along the liquid surface. According to such a device, it ispossible to transfer the monolayer particle film F₁ having a large areato the substrate S₁ more stably.

That is, according to such a device, the monolayer particle film F₁ canbe compressed to a preferred diffusion pressure (density) whilemeasuring the surface pressure of the monolayer particle film F₁, andalso can be moved at a constant speed towards the substrate S₁.Therefore, the transfer of the monolayer particle film F₁ from theliquid surface to the substrate S₁ proceeds smoothly, troubles in whichonly the monolayer particle film F₁ having a small area can betransferred to the substrate S₁ or the like are less likely to occur.The diffusion pressure is preferably from 5 mNm⁻¹ to 80 mNm⁻¹, and morepreferably from 10 mNm⁻¹ to 40 mNm⁻¹. If the diffusion pressure iswithin such a range, the monolayer particle film F₁ in which eachparticle is close-packed two-dimensionally with higher accuracy can beeasily obtained. In addition, the rate for pulling the substrate S₁upward is preferably from 0.5 mNn⁻¹ to 20 mm/minute. The temperature ofthe underlying water is generally from 10° C. to 30° C. as previouslydescribed. It should be noted that the LB trough device can be obtainedas a commercially available product.

As described above, although it is preferable to transfer the monolayerparticle film F₁ to the substrate S₁ in a state in which each particleis close-packed two-dimensionally with an accuracy as high as possible,no matter how careful the work is carried out, 100% completeclose-packing cannot be achieved, and the particles transferred to thesubstrate S₁ becomes a polycrystalline state. As a result, through thesteps to be described later, it becomes possible to ultimately form, onthe substrate S₁, an uneven structure having a plurality of areas inwhich the central points of seven adjacent convex portions are alignedcontinuously in a positional relationship so as to become six verticesand intersection point of diagonal lines of a regular hexagon.(Fixing Step)

Although it is possible to transfer the monolayer particle film F₁ ofthe particles M₁ to the substrate S₁ by the transfer step, following thetransfer step, a fixing step for fixing the transferred monolayerparticle film F₁ to the substrate S₁ may be carried out. With only thetransfer step, there is a possibility that the particles M₁ would moveover the substrate S₁ during the particle etching step and the substrateetching step described later. In particular, such a possibilityincreases at the final stage of the substrate etching step in which thediameter of each particle M₁ gets smaller gradually.

By carrying out a fixing step for fixing a monolayer particle film onthe substrate S₁, possibility of the particles M₁ moving on thesubstrate S₁ is suppressed, and etching can be conducted more stably andat a high accuracy.

As a method for the fixing step, there are a method using a binder and asintering method.

In the method using a binder, a binder solution is supplied to the flatsurface X side of the substrate S₁ on which a monolayer particle filmhas been formed, and is infiltrated between the particles M₁constituting the monolayer particle film and the substrate S₁.

The amount of binder used is preferably from 0.001 times to 0.02 timesthe mass of the monolayer particle film. If the amount is within such arange, particles can be fixed sufficiently without causing the problemof excessive amount of binder blocking between the particles M₁ toadversely affect the accuracy of the monolayer particle film. In thosecases where a large amount of binder solution is supplied, after thebinder solution has infiltrated, the excess of the binder solution maybe removed by using a spin coater or tilting the substrate S₁.

As a binder, it is possible to use the metal alkoxysilanes exemplifiedearlier as a hydrophobizing agent, common organic binders and inorganicbinders or the like, and after the binder solution has infiltrated, aheating treatment may be performed as appropriate depending on the typeof the binder. When a metal alkoxysilane is used as a binder, it ispreferable to conduct a heat treatment under conditions of 40° C. to 80°C. for 3 minutes to 60 minutes.

When employing the sintering method, it is sufficient to heat thesubstrate S₁ on whicha monolayer particle film has been formed so thateach particle M₁ constituting the monolayer particle film is fused tothe substrate S₁. Although the heating temperature may be determined inaccordance with the material of the particles M₁ and the material of thesubstrate S₁, since the particles M₁ having a particle size of 1 μmφ orless start the interface reaction at a lower temperature than theoriginal melting point of the material, sintering is completed at arelatively low temperature side. When the heating temperature is toohigh, the fused area of the particle increases, and, as a result, theshape of the monolayer particle film changes, which may adversely affectthe accuracy.

In addition, when the heating is conducted in air, since the substrateS₁ and the particles M₁ may be oxidized, in the case of employing thesintering method, it is necessary to set the conditions by taking thepossibility of such oxidation into consideration. For example, if asilicon substrate is used as the substrate S₁ and is sintered at 1,100°C., a thermally oxidized layer having a thickness of about 200 nm isformed on the surface of the substrate S₁. It is easy to avoid oxidationwhen heated in N₂ gas or argon gas.

[Particle Arranging Step by Other Methods]

The particle arranging step is not particularly limited as long as adeviation D(%) of the arrangement can be set from 1.0% or more to 15% orless, and, in addition to the LB method, the following method can beemployed.

1) A method in which a substrate is immersed in a suspension ofcolloidal particles, and then particle layers of a second or higherlayers are removed while leaving only the particle layer of the firstlayer which is electrostatically bonded to the substrate (particleadsorption method), thereby providing an etching mask composed of amonolayer particle film on the substrate (see Japanese Unexamined PatentApplication, First Publication No. Sho 58-120255).

2) A method in which a binder layer is formed on a substrate, adispersion liquid of particles is applied thereon, and then the binderlayer is softened by heating, thereby embedding only a particle layer ofthe first layer in the binder layer to wash off the excess particles(see Japanese Unexamined Patent Application, First Publication No.2005-279807).

[Particle Etching Step]

In the particle etching step, a plurality of particles M₁ arranged inconditions so as not to substantially etch the substrate S₁ are dryetched. As a result, as shown in FIG. 3B, only particles M₁ aresubstantially etched to form particles M₁₁ having a small particlediameter, and gaps are provided between the particles M₁₁. On the otherhand, the substrate S₁₁ after the particle etching step is substantiallythe same as the substrate S₁, while no substantial irregularities areformed on a flat surface X₁₁ which is one surface of the substrate S₁₁,and thus the flat surface X₁₁ and the flat surface X₁ are equivalent.

As the conditions in which the substrate S₁ is not substantially etched,dry etching selection ratio in the following equation (2) is preferably25% or less, more preferably 15% or less, and still more preferably 10%or less.Dry etching selectivity[%]=(dry etching rate of substrate S ₁)/(dryetching rate of particle M ₁)×100  (2)

In order to achieve such dry etching conditions, an etching gas may beselected appropriately. For example, in those cases where a substrate Sis sapphire and particles M₁ are silica, if dry etching is carried outusing one or more gases selected from CF₄, SF₆, CHF₃, C₂F₆, C₃F₈, CH₂F₂,O₂ and NF₃, the particle M₁ can be etched with little adverse effect onthe substrate S₁. Alternatively, when a substrate S is sapphire andparticles M₁ are titania (TiO₂), if dry etching is carried out using oneor more gases selected from CF₄, SF₆, CHF₃, C₂F₆, C₃F₈, CH₂F₂, O₂ andNF₃, the same effect as described above can be achieved. Alternatively,when a substrate S is sapphire and particles M₁ are polystyrene, if dryetching is carried out using one or more gases selected from CF₄, SF₆,CHF₃, C₂F₆, C₃F₈, CH₂F₂, O₂ and NF₃, the same effect as described abovecan be achieved. Alternatively, when a substrate S is silicon andparticles M₁ are polystyrene, if dry etching is carried out using O₂gas, the same effect as described above can be achieved.

Since the particles M₁₁ following the particle etching step are used asan etching mask in the subsequent substrate etching step, it isnecessary to sufficiently leave the diameter (hereinafter, referred toas “height”) of the substrate S₁ in the thickness direction (verticaldirection). In addition, in order to prepare the etching mask in whichthe particles M₁₁ are sufficiently spaced, it is necessary that the size(hereinafter, referred to as “area”) of the particle M₁₁ in the planedirection (horizontal direction) of the substrate S₁ be sufficientlysmall. Therefore, the particle etching step is preferably carried outunder the conditions to reduce the area while suppressing the reductionin height.

In order to achieve the above condition, it is sufficient to set thebias power to a lower level, or set the pressure to a low pressure.

[Substrate Etching Step]

In the substrate etching step, the substrate S₁₁ following the particleetching step is dry etched using the particle M₁₁ after the particleetching step as an etching mask. Since the substrate S₁₁ is firstexposed to the etching gas in the gaps between the particles M₁₁, theseportions are etched in advance while maintaining the flatness. Inaddition, since the particles M₁₁ are also etched gradually becomesmall, etching of the substrate S₁₁ proceeds gradually from the lowerpart of the periphery toward the lower part of the center of eachparticle M₁₁. As a result, as shown in FIG. 3C, the particles M₁₁ becomeparticles M₁₂ having an even smaller particle diameter. In addition, ona substrate S₁₂ at this time point, a plurality of convex portions Y₁₂of a truncated cone shape having the lower side of each particle M₁₂ asa top surface are formed. The void between the convex portions Y₁₂(bottom surface of the recess portion) substantially corresponds to thevoid between the particles M₁₁, and that portion becomes a flat surfaceX₁₂.

If the substrate etching step is allowed to proceed further, eachparticle M₁₂ ultimately disappears by etching. As a result, as shown inFIG. 3D, on a substrate S₁₃ after completion of the substrate etchingstep, a plurality of convex portions Y₁₃ of a truncated cone shapehaving the lower side of the central part of each particle M₁₂ as avertex are formed. The void between the convex portions Y₁₃ (bottomsurface of the recess portion) becomes a flat surface X₁₃. The flatsurface X₁₃ substantially corresponds to the void between the particlesM₁₁ and the flat surface X₁₂, and becomes a bottom surface of a recessportion which is even deeper than the flat surface X₁₂.

In the substrate etching step, the dry etching rate of the substrate S₁₂(substrate S₁) needs to be greater than the etching rate of theparticles M₁₂ (particles M₁), and it is required that the dry etchingselection ratio in the aforementioned equation (2) be greater than 100%.The dry etching selection ratio in the aforementioned equation (2) inthe substrate etching step is preferably 200% or more, and morepreferably 300% or more.

It should be noted that for such etching conditions, the etching gasused in the reactive etching may be selected appropriately. For example,when the device substrate S₁ is sapphire and the particles M₁ aresilica, one or more gases selected from the group consisting of Cl₂,Br₂, BCl₃, SiCl₄, HBr, HI, HCl and Ar may be used as an etching gas.

As an available etching device, be one there is no particularrestriction on the specifications such as the plasma generation method,the structure of the electrode, the structure of the chamber and thefrequency of the high-frequency power supply, as long as it is capableof anisotropic etching and generating a minimum of bias field of about20 W, such as a reactive ion etching apparatus and an ion beam etchingapparatus.

The substrate etching step is preferably carried out by holding thetemperature inside the chamber from 60° C. to 200° C., and morepreferably carried out by holding the temperature from 80° C. to 150° C.

By holding the temperature inside the chamber to the above-mentionedtemperature, since the etching rate of the substrate is increased andthe handling is easy, it is possible to improve the manufacturingefficiency.

In those cases where the substrate is a sapphire substrate, it isparticularly preferable to carry out the substrate etching step at theabove temperature.

The shape of the convex portion Y₁₃ can be adjusted depending on thebias power, the pressure in the vacuum chamber and the type of theetching gas. For example, if the pressure is lowered, a shape with agradual inclination angle is obtained.

It should be noted that it is also possible to end the substrate etchingstep at a stage depicted in FIG. 3C to form a convex portion with atruncated cone shape. In that case, the remaining particles M₁₂ can beremoved by a chemical removal method using an etching gas havingetchability with respect to the particle M₁₂ and etching resistance withrespect to the substrate S₁₂, or a physical removal method using a brushroll washing machine and the like.

A pitch of the uneven structure provided on the substrate S₁ in thepresent embodiment is equivalent to the most frequent pitch B betweenthe particles M₁ described above. Since the degree of close packing ofthe arrangement of the particles M₁ in FIG. 3A is high, by appropriatelyselecting an average particle diameter A of particles M₁, it is possibleto form an uneven structure having a desired pitch with good accuracy.

In addition, since the particle etching step is carried out prior to thesubstrate etching step, the space between the convex portions, that is,the bottom surface of the recess portion can be formed as a flatsurface. For this reason, a semiconductor layer can be grown stably on aflat surface. Therefore, a substrate for a semiconductor light emittingdevice which is less likely to generate crystal defects in thesemiconductor layer can be prepared.

According to the manufacturing method of the present embodiment, thecost and time required for producing a relatively small uneven structurewith a pitch of 1 μm or less (sub-micron pitch) may be less than thecost and time required for producing a relatively large uneven structurewith a pitch of several micrometers. This is due to the fact that themanufacturing cost of the particles to become an etching mask reduces asthe particle diameter is reduced, and that the process time required forthe dry etching step shortens as the particle diameter is reduced. Itshould be noted that the cost of the device for producing a relativelysmall uneven structure with a pitch of 1 μm or less and that of thedevice for producing a relatively large uneven structure with a pitch ofseveral micrometers are equivalent.

In addition, according to the manufacturing method of the presentembodiment, an uneven structure having an arrangement like apolycrystalline structure in which a macroscopic lattice orientation israndom (that is, the ratio of the maximum value and the minimum value ofthe FFT fundamental wave is small) can be provided to the substrate S₁.

<Semiconductor Light Emitting Device>

A semiconductor light emitting device of the present embodiment includesa semiconductor light emitting device substrate of the presentembodiment, a semiconductor functional layer laminated on the surfacewhere the uneven structure has been formed, a p-type electrode and ann-type electrode. The semiconductor functional layer at least includes alight emitting layer.

The semiconductor functional layer is preferably composed of a groupIII-V nitride semiconductor group in which a group V element isnitrogen. For example, GaN, InGaN, AlGaN, InAlGaN, GaAs, AlGaAs,InGaAsP, InAlGaAsP, InP, InGaAs, InAlAs, ZnO, ZnSe, ZnS and the like canbe mentioned. This is because there is a need to form a group III-Vnitride semiconductor on a substrate such as sapphire.

Typical examples of group III-V nitride semiconductors include galliumnitride and indium nitride. Although aluminum nitride is strictly aninsulator, in the present embodiment, in accordance with the conventionin the field of the semiconductor light emitting device, it is treatedas falling within the category of III-V nitride semiconductor.

The layer constitution of the semiconductor functional layer ispreferably a constitution composed at least of an n-type conductivelayer, a p-type conductive layer and a group III-V nitride semiconductorlayer having a light emitting layer sandwiched between these layers. Asthe light emitting layer, a light emitting layer composed of a groupIII-V nitride semiconductor represented by In_(x)Ga_(y)Al_(z)N (wherein0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1) is preferred.

In the group III-V nitride semiconductor functional layer, in additionto the n-type conductive layer, the p-type conductive layer and thelight emitting layer sandwiched between these layers, a monolayer ormultilayer (including cases where it is a thick film layer or asuperlattice thin film layer) required for making these layers a highquality crystal may also be included in some cases.

For example, there are also cases where a buffer layer is included.

In addition, each of the above-mentioned layers may also be composed ofa plurality of layers, respectively.

Specific examples of the semiconductor functional layer include amultilayer film formed by sequentially laminating a buffer layercomposed of GaN, AIN or the like, an n-type conductive layer (claddinglayer) composed of n-GaN, n-AlGaN or the like, a light emitting layercomposed of InGaN, GaN or the like, a p-type conductive layer (claddinglayer) composed of undoped GaN, p-GaN or the like, and a cap layercomposed of Mg-doped AlGaN, Mg-doped GaN (see, for example, JapaneseUnexamined Patent Application, First Publication No. Hei 6-260682,Japanese Unexamined Patent Application, First Publication No. Hei7-15041, Japanese Unexamined Patent Application, First Publication No.Hei 9-64419 and Japanese Unexamined Patent Application, FirstPublication No. Hei 9-36430).

It should be noted that as the n-type electrode and the p-type electrodefor supplying electric current to the light emitting layer, it ispossible to use an electrode made of a metal such as Ni, Au, Pt, Pd, Rh,Ti and Al.

Functions of the semiconductor functional layer preferably include anactivity for recombining the n-type conductivity, p-type conductivityand a carrier. A laminated structure in the semiconductor functionallayer may be a double heterostructure in which an active layer issandwiched between an n-type semiconductor layer and a p-typesemiconductor layer, or may be a multiple quantum well structure inwhich a plurality of quantum well structures are superimposed.

In the semiconductor light emitting device of the present embodiment, inorder to adjust the emission wavelength, it is also possible to laminatea wavelength conversion layer for converting the wavelength of lightemitted from the light emitting layer to the light extraction side ofthe semiconductor functional layer to the long wavelength side than thewavelength of the emitted light. For example, in the case of a topemission type device, since the light emitted by the light emittinglayer is extracted from the p-type electrode side, it is possible toarrange the wavelength conversion layer between the light emitting layerand the p-type electrode. Alternatively, the wavelength converting layermay be arranged outside the p-type electrode (outside the device) (inthis case, a phosphor is included in a resin embedding an LED device).Alternatively, in the case of a bottom emission type device, since thelight emitted by the light emitting layer is taken out through thesubstrate, it is possible to arrange the wavelength conversion layerbetween the light emitting layer and the substrate. In addition, inthose cases where the light emitted by the light emitting layer is takenout through the substrate, the wavelength conversion layer can bearranged on a surface opposite to a surface of the substrate on whichthe semiconductor light emitting device is provided. In this case, it isalso possible to place the wavelength conversion layer by a method ofincluding a phosphor in a resin embedding an LED device.

For example, when the emission wavelength of the light emitting layercontains a large amount of emission energy of the ultraviolet region, byincluding a blue phosphor that emits fluorescence with a peak wavelengthof 410 nm to 483 nm, a green phosphor that emits fluorescence with apeak wavelength of 490 nm to 556 nm and a red phosphor that emitsfluorescence with a peak wavelength of 585 nm to 770 nm in thewavelength conversion layer, it is possible to obtain white extractedlight suitable for illumination. In addition, if the emission wavelengthof the light emitting layer contains a large amount of emission energyof the blue region, by including an yellow phosphor that emitsfluorescence with a peak wavelength of 570 nm to 578 nm in thewavelength conversion layer, it is possible to obtain white extractedlight suitable for illumination.

<Method of Manufacturing a Semiconductor Light Emitting Device>

A method of manufacturing a semiconductor light emitting deviceaccording to the present embodiment includes a step of obtaining a lightemitting device substrate by the method of manufacturing the lightemitting device substrate according to the present embodiment, and astep of laminating a semiconductor function layer including at least alight emitting layer on a surface of the resulting light emitting devicesubstrate on which an uneven structure has been formed.

[Semiconductor Functional Layer Lamination Step]

For a method of laminating a semiconductor functional layer on asemiconductor light emitting device substrate, a known epitaxial growthmethod such as an MOVPE (metal-organic vapor phase epitaxy) method, anMBE (molecular beam epitaxy) method and an HVPE (hydride vapor phaseepitaxy) method can be used. Examples of the epitaxial growth methodinclude a vapor phase epitaxial growth method, a liquid phase epitaxialgrowth method and a molecular beam epitaxial growth method. In areactive sputtering method, a target composed of constituent elements ofa compound semiconductor layer is sputtered, and a material for formingthe semiconductor layer is produced by a reaction of the particlessputtered from the target with impurities in the vapor phase. A methodfor forming an n-type semiconductor layer may be any method as long asit is an epitaxial growth method or reactive sputtering method in whichan n-type impurity is added. A method for forming a p-type semiconductorlayer may be any method as long as it is an epitaxial growth method orreactive sputtering method in which a p-type impurity is added.

In the liquid phase epitaxial growth method, using a supersaturatedsolution containing a material for forming the compound semiconductorlayer while maintaining the equilibrium of a solid phase and a liquidphase, the material for forming the compound semiconductor layer isgrown as a crystal on a light emitting structure forming surface of thesemiconductor light emitting device substrate. In the vapor phaseepitaxial growth method, an atmosphere in which material gas flowsgenerates a material for forming the compound semiconductor layer, andthe material for forming the compound semiconductor layer is grown as acrystal on a light emitting structure forming surface. In the molecularbeam epitaxial growth method, a beam of molecules or atoms composed of aconstituent element of the compound semiconductor layer is irradiatedonto a light emitting structure forming surface, thereby growing amaterial for forming the compound semiconductor layer as a crystal onthe light emitting structure forming surface. Among these, the halidevapor phase epitaxy method using a hydride such as AsH₃ and PH₃ as agroup V raw material is preferred in terms of a large thickness of thegrowing compound semiconductor layer.

As a group III material, for example, trialkyl gallium represented by ageneral formula R₁R₂R₃Ga (here, R₁, R₂ and R₃ represent a lower alkylgroup) such as trimethyl gallium [(CH₃)₃Ga, hereinafter sometimesreferred to as TMG] and triethyl gallium [(C₂H₅)₃Ga, hereinaftersometimes referred to as TEG], trialkyl aluminum represented by ageneral formula R₁R₂R₃Al (here, R₁, R₂ and R₃ represent a lower alkylgroup) such as trimethylaluminum [(CH₃)₃Al, hereinafter sometimesreferred to as TMA], triethylaluminum [(C₂H₅)₃Al, hereinafter sometimesreferred to as TEA] and triisobutyl aluminum [(i-C₄H₉)₃Al],trimethylamine alane [(CH₃)₃N: A1H₃], trialkyl indium represented by ageneral formula R₁R₂R₃In (here, R₁, R₂ and R₃ represent a lower alkylgroup) such as trimethylindium [(CH₃)₃In, hereinafter sometimes referredto as TMI] and triethyl indium [(C₂H₅)₃In]), those obtained bysubstituting one or two alkyl groups from trialkyl indium with a halogenatom, such as diethyl indium chloride [(C₂H₅)₂InCl], and halogenatedindium represented by a general formula InX₃ (X represents a halogenatom) such as indium chloride [InCl₃] and the like can be mentioned.These may be used alone or may be used as a mixture.

As a group V material, for example ammonia, hydrazine, methylhydrazine,1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine,ethylenediamine and the like can be mentioned. These can be used aloneor as a mixture in any combination. Among these materials, ammonia andhydrazine are preferred since they do not contain carbon atoms withinthe molecule and the level of carbon contamination into thesemiconductor is low.

In the MOVPE method, as an atmospheric gas and a carrier gas of anorganometallic material during growth, a gas such as nitrogen, hydrogen,argon and helium can be used alone or as a mixture, and hydrogen andhelium are preferred.

According to the present embodiment, the uneven structure of thesubstrate has moderate randomness. Therefore, it is possible to obtain asemiconductor light emitting device with which a sufficient lightextraction efficiency is obtained while the problem of increases in thecolor shift and in-plane anisotropy is prevented. In addition, since asemiconductor is laminated on a substrate in which a flat surface isformed between the convex portions, it is possible to stably grow asemiconductor layer on the flat surface. Therefore, the crystal defectsin the semiconductor layer are less likely to occur.

[Second Embodiment]

With reference to FIG. 6 to FIG. 13, a semiconductor light emittingdevice substrate, a semiconductor light emitting device, a method ofmanufacturing a semiconductor light emitting device substrate, and amethod of manufacturing a semiconductor light emitting device accordingto the present embodiment will be described.

[Semiconductor Light Emitting Device Substrate]

As shown in FIG. 6, a semiconductor light emitting device substrate(hereinafter, referred to as a device substrate 211B) includes, as oneside surface, a light emitting structure forming surface 211S. In themanufacturing process of the semiconductor light emitting device, alight emitting structure is formed on the light emitting structureforming surface 211S.

As a material for forming the device substrate 211B, the material of thesubstrate described in the first embodiment can be used. The lightemitting structure forming surface 211S has crystallinity in itselfwhich is suitable for providing crystallinity to the light emittingstructure.

The light emitting structure forming surface 211S includes an unevenstructure constituted of a large number of fine irregularities. Fineirregularities are repeated in the direction along which the lightemitting structure forming face 211S spreads. The uneven structureincluded in the light emitting structure forming surface 211S isconstituted of a large number of convex portions 212, a large number ofbridge portions 213 and a large number of flat portions 214.

Each of the number of flat portions 214 is a flat surface being extendedalong one crystal plane, and is arranged on one plane. When the crystalsystem of the device substrate 211B is hexagonal, the flat portion 214is, for example, a flat surface obtained by continuation of a singleplane selected from the group consisting of a c-plane, m-plane, a-planeand r-plane. When the crystal system of the device substrate 211B iscubic, the flat portion 214 is, for example, a flat surface obtained bycontinuation of a single plane selected from the group consisting of a(001) plane, (111) plane and (110) plane. It should be noted that thecrystal plane included in the flat portion 214 may be a higher indexplane than the index plane described above, as long as it is a singlecrystal plane suitable for providing crystallinity to the light emittingstructure. The crystal plane included in each of the plurality of flatportions 214 facilitate provision of crystallinity to the semiconductorlayer on the light emitting structure forming surface 211S.

[Protrusion 12]

Each of the numerous convex portions 212 protrudes from the flat portion214 connected to the convex portion 212, and also has a shape that getsnarrower from the base end to be connected to the flat portion 214toward the apex. Each of the plurality of convex portions 212 has ahemispherical shape.

It should be noted that the shape of the convex portions 212 is notlimited to the hemispherical shape, and it may be a conical shape or maybe a pyramid shape. In addition, bus that passes through the apex of theconvex portion 212 and appears when the convex portion 212 is cut by aplane perpendicular to the light emitting structure forming surface 211Sin the cross-section thereof may be a curve. The shape of the convexportion 212 may be a multistage shape that gets narrower from the baseend toward the apex, and may even be shape that gets thick once on theway from the base end to the apex. The shapes of each of a large numberof convex portions 212 may be different from each other.

An interval between the convex portions 212 adjacent to each other is apitch of the convex portion 212. The pitch of the convex portions 212may be the same as that of the first embodiment. As one aspect, the mostfrequent value of the pitch is preferably equal to or more than 100 nmand equal to or less than 5 μm. If the pitch of the convex portion 212is equal to or more than 100 nm and equal to or less than 5 μm, to anextent so that the total reflection of light at the light emittingstructure forming surface 211S is suppressed, on the light emittingstructure forming surface 211S, the convex portions 212 are formed inthe arrangement and density required therefor. In this case, the balancebetween the convex portion 212 and the flat portion 214 is appropriatelydesigned. In addition, if the most frequent value of the pitch of theconvex portion 212 is 5 μm or less, visibility of a large number ofprotrusions 212 is sufficiently suppressed, and an unnecessary increasein the thickness of the device substrate 211B is also suppressed.

The most frequent value of the pitch can be obtained by the method ofdetermining the most frequent pitch P described in the first embodiment.For example, as shown below, it can be determined by image processingbased on the AFM image. First, for a rectangular region selectedarbitrarily in the light emitting structure forming surface 211S, an AFMimage is obtained. At this time, in the rectangular region from whichthe AFM image is obtained, the length of one side of the rectangularregion is 30 to 40 times as long as the most frequent value of thepitch. Next, by the waveform separation of the AFM image using a Fouriertransform, a fast Fourier transform image based on the AFM image isobtained. Then, the distance between the zero-order peak and the primarypeak in the fast Fourier transformed image is obtained, and thereciprocal of the distance is treated as a pitch of the convex portion212 in one rectangular region. Then, the pitch is measured for therectangular regions in 25 or more locations that are different from eachother, and an average value of the thus obtained measured value is amost frequent value of the pitch of the convex portion 212. It should benoted that the rectangular regions are preferably separated from eachother by at least 1 mm, and more preferably separated by 5 mm to 1 cm.

The height from the flat portion 214 in each of a large number of convexportions 212 may be the same as that of the first embodiment. As oneaspect, the height from the flat portion 214 in each of a large numberof convex portions 212 is preferably equal to or more than 50 nm andequal to or less than 300 nm. If the height of the plurality of convexportions 212 is equal to or more than 50 nm and equal to or less than300 nm, the total reflection of light in the light emitting structureforming surface 211S is easily suppressed. If the height of the convexportion 212 is equal to or more than 50 nm and equal to or less than 300nm, in a semiconductor layer to be formed on the light emittingstructure formed surface 211S, the occurrence of deposition defectscaused by the formation of the convex portion 212 is suppressed.

The most frequent value of the height of the convex portion 212 isdetermined, for example, as shown below, by image processing based onthe AFM image. First, for a rectangular region selected arbitrarily inthe light emitting structure forming surface 211S, an AFM image isobtained, and from the AFM image, a cross-sectional shape of an unevenstructure is obtained. Next, for five or more convex portions 212 thatare arranged in series in the cross-sectional shape, the differencebetween the height of the vertex in the convex portion 212 and theheight of the flat portion 214 connected to the convex portion 212 ismeasured. Then, the height of the convex portion 212 is also measured inthe same manner for the rectangular regions in 5 or more locations thatare different from each other, and the height of 25 or more convexportions 212 is measured in total. It should be noted that therectangular regions are preferably separated from each other by at least1 mm, and more preferably separated by 5 mm to 1 cm. Then, a profile inthe equatorial direction using a two-dimensional Fourier transform imageis created, and the most frequent value of the height of the convexportion 212 is obtained from the reciprocal of the primary peak thereof.

[Bridge Portion 213]

In the present embodiment, a bridge portion can be configured in amanner so as to connect the adjacent convex portions 212 with eachother. Although it is possible to obtain the optical effects and theeffect of mechanical strength to be described later by providing thebridge portion, even if the bridge portion is not provided, since therange of the flat portion 214 is expanded by the particle size reductionof the mask particles, it is possible to effectively carry out anepitaxial growth in the LED forming step afterwards.

Each of a large number of the bridge portions 213 protrudes from a flatportion 214 to be connected to the bridge portion 213, and also linksbetween the convex portions 212 that are adjacent to each other. Theheight of each of a large number of the bridge portions 213 is lowerthan the height of the convex portion 212, and also has a ridge shapethat connects the centers of the convex portions 212 having ahemispherical shape. It should be noted that the shape of the bridgeportion 213 is not limited to a linear shape, and may be a curved shapeor a broken line shape. The shape of each of a large number of thebridge portions 213 may be different from each other. The bridge portion213 includes a top surface 213T. The top surface 213T includes a flatsurface.

The length along the longitudinal direction of the bridge portion 213 ispreferably equal to or more than 50 nm and equal to or less than 300 nm.If the length along the longitudinal direction of the bridge portion 213is equal to or more than 50 nm and equal to or less than 300 nm, thetotal reflection of light at the light emitting structure formingsurface 211S is easily suppressed. The length along the transversedirection of the bridge portion 213 is preferably equal to or more than10 nm and equal to or less than 100 nm. If the length along thetransverse direction of the bridge portion 213 is equal to or more than10 nm and equal to or less than 100 nm, the total reflection of light atthe light emitting structure forming surface 211S is easily suppressed.In addition, the mechanical strength of the bridge portion 213 issecured to an extent so as to sufficiently endure the film stress of thelight emitting structure.

As shown in FIG. 7, in plan view of the light emitting structure formingsurface 211S, a plurality of convex portions 212 include a plurality ofconvex portion pairs TP2. One convex portion pair TP2 is constituted oftwo convex portions 212 that are adjacent to each other, and the twoconvex portions 212 included in one convex portion pair TP2 areconnected by a single bridge portion 213. In the light emittingstructure forming surface 211S, one flat portion 214 is surrounded bythree convex portion pairs TP2.

A plurality of convex portions 212 include a plurality of convex portiongroups TG2. One convex portion group TG2 is constituted of six convexportion pairs TP2. In one convex portion group TG2, one of the convexportions 212 in the six convex portion pairs TP2 is common with eachother. Seven convex portions 212 that constitute one convex portiongroup TG2 have a hexagonal packing structure. In the convex portiongroup TG2, 6 convex portions 212 are arranged at six vertices of ahexagonal shape and one convex portion 212 is also placed at a portionsurrounded by the six convex portions 212. That is, in each of theplurality of convex portion groups TG2, in the periphery of one convexportion 212 to become the center, six convex portions 212 are arrangedequally. Then, from the one convex portion 212 which is the centertoward the other convex portions 212, six bridge portions 213 areextended radially. In one convex portion group TG2, the height of eachof the six bridge portions 213 tends to be low as the interval betweenthe convex portions 212 that are connected by the bridge portion 213increases.

If the light emitting structure forming surface 211S is configured so asto include a plurality of convex portion groups TG2, the effect ofsuppressing the total reflection by the convex portion 212 is enhanced.Further, concentration of the film stress of the light emittingstructure to be formed on the light emitting structure forming surface211S on one convex portion 212 can also be suppressed. In addition, themechanical strength required for the convex portion 212 can also besuppressed.

A plurality of convex portions 212 include a plurality of convex portionteams TL2. Each of the plurality of convex portion teams TL2 isconstituted of two or more convex portion groups TG2. In each of theplurality of convex portion teams TL2, two convex portion groups TG2that are different from each other share two or more convex portions 212with each other. In each of the plurality of convex portion teams TL2,any one of preferably any two of, and more preferably all of a directionin which the convex portion groups TG2 are aligned, an area occupied byone convex portion team TL2 and a shape of one convex portion team TL2are different from each other. That is, in the light emitting structureforming surface 211S, each of the plurality of convex portion teams TL2is arranged at random including the size and shape thereof. In oneconvex portion team TL2, the height of each of the plurality of bridgeportions 213 preferably gets low, as the interval between the convexportions 212 that are connected by the bridge portion 213 increases.

If the light emitting structure forming surface 211S is configured so asto include a plurality of convex portion teams TL2, a fine unevenstructure has a moderate randomness to an extent so that the refractionof light entering the light emitting structure forming surface 211S isaveraged inside the light emitting structure forming surface 211S.Therefore, the effect of suppressing the total reflection is averaged bythe light emitting structure forming surface 211S. In addition, sinceone bridge portion 213 is formed for each one of the convex portionpairs TP2, the effect of suppressing the total reflection is furtherenhanced. Furthermore, while a large number of such bridge portions 213are formed, one flat portion 214 is surrounded by three bridge portions213. For this reason, unevenly high distribution of the bridge portion213 in one place is suppressed, and extremely low distribution of theflat portion 214 in one place can also be suppressed. As a result, it ispossible to suppress the crystallinity of the light emitting structurebeing extremely inferior in one place, and the total reflection at thelight emitting structure forming surface 211S can also be suppressed.

It should be noted that the light emitting structure forming surface211S may have an isolated convex portion group TG2 or may have anisolated convex portion 212, in addition to the plurality of convexportion teams TL2. Further, each of the plurality of convex portionteams TL2 may have the same size as each other, and may have the sameshape as each other. In addition, each of the plurality of convexportion teams TL2 may be configured so that the directions in which theconvex portion groups TG2 are aligned are the same with each other, aslong as they are configured to be separated from each other.

As shown in FIG. 8, the height of the vertex of the convex portion 212with respect to the flat portion 214 is a convex portion height HT₂. Inaddition, the height of a top surface 213T of the bridge portion 213with respect to the flat portion 214 is a bridge height HB₂. In thosecases where the bridge portions are actively provided, it is preferablethat the bridge height HB₂ be lower than the convex portion height HT₂,and lower than half of the convex portion height HT₂. More specifically,a ratio HB₂/HT₂ is preferably in the range of 0.01 to 0.40, and morepreferably in the range of 0.05 to 0.20. The bridge height HB₂ ispreferably constant over substantially the whole of the bridge portion213 along the direction in which the bridge portion 213 extends.

As shown in FIG. 9, the bridge height HB₂ is also constant along adirection that intersects with the direction in which the bridge portion213 extends. The top surface 213T of the bridge portion 213 includes aflat surface. The flat surface extends along the direction in which thebridge portion 213 extends and also continues along the direction thatintersects with the direction in which the bridge portion 213 extends.The top surface 213T of the bridge portion 213 includes a flat surfaceextending along one crystal plane, as the flat portion 214.

When the crystal system of the device substrate 211B is hexagonal, thetop surface 213T of the bridge portion 213 is, as the flat portion 214,for example, a flat surface obtained by continuation of a single planeselected from the group consisting of a c-plane, m-plane, a-plane andr-plane. When the crystal system of the device substrate 211B is cubic,the top surface 213T of the bridge portion 213 is, also as the flatportion 214, for example, a flat surface obtained by continuation of asingle plane selected from the group consisting of a (001) plane, (111)plane and (110) plane.

If the top surface 213T of the bridge portion 213 is configured so as tohave the crystal plane as described above, in addition to the flatportion 214, also in the top surface 213T of the bridge portion 213,provision of crystallinity to the semiconductor layer is facilitated.For this reason, even when it is configured so that a portion of theflat portion 214 is used as the bridge portion 213, it is possible tosuppress reduction in the crystallinity of the semiconductor layer dueto this.

[Method of Manufacturing the Device Substrate 211B]

A method of manufacturing a semiconductor light emitting devicesubstrate includes: a particle arranging step for arranging a pluralityof particles on a substrate; a particle etching step (etching step ofmonolayer particle film F₁) for dry etching the aforementioned pluralityof particles arranged to provide a void between the particles in acondition by which the aforementioned particles are etched while theaforementioned substrate is not etched substantially; and a substrateetching step (etching step of light emitting structure forming surface11S) for dry etching the aforementioned substrate by using the pluralityof particles after the aforementioned particle etching step as anetching mask, thereby forming an uneven structure on one surface of theaforementioned substrate. Hereinafter, each step included in the methodof manufacturing a semiconductor light emitting device substrate will bedescribed in the order of treatment, although for the particle arrangingstep, because it can be carried out by the same method as in the firstembodiment, the description thereof will be omitted.

[Etching Step of Monolayer Particle Film F₁]

An etching step of a monolayer particle film F₁ can be carried outbasically by the same method as in the first embodiment.

As one aspect, as shown in FIG. 10, the monolayer particle film F₁constituted of particles M₁ of a monolayer is formed on the lightemitting structure forming surface 211S. The monolayer particle film F₁has a hexagonal packing structure of the particles M₁ having a diameterR21. One hexagonal packing structure is formed of seven particles M₁. Inthe hexagonal packing structure, six particles M₁ are arranged at sixvertices of a hexagonal shape, and one particle M₁ is filled in aportion surrounded by the six particles M₁. That is, in one hexagonalpacking structure, in the periphery of one particle M₁ to become thecenter, six particles M₁ are arranged equally.

The hexagonal packing structure includes three particles M₁ arranged atthree vertices of a triangle. A region surrounded by three particles M₁when viewed from the normal direction of the substrate is a minimum voidin the monolayer particle film F₁. When viewed from the normal directionof the substrate, the light emitting structure forming surface 211S hasa first exposed portion S21 exposed to the outside through this minimumvoid.

As shown in FIG. 11, in the monolayer particle film etching step, theparticles M₁ constituting the monolayer particle film F₁ are etchedunder etching conditions by which the device substrate 211B is notsubstantially etched. At this time, the particle size of the particlesM₁ constituting the monolayer particle film F₁ is reduced to a diameterR22 by selective etching. By the reduction of particles M₁ in size,between the particles M₁ that are adjacent to each other, a new void isformed. The light emitting structure forming surface 211S has a secondexposed portion S22 exposed to the outside through this new void. Thatis, by newly forming the second exposed surface S22 in the periphery ofthe first exposed surface S21, the first exposed surface S21 becomes asingle continuous exposed surface. It should be noted that the lightemitting structure forming surface 211S is not substantially etched, andkeeps the same state as before the reduction of particle size of theparticles M₁.

In the etching conditions by which the light emitting structure formingsurface 211S is not substantially etched, the ratio of the etching rateof the light emitting structure forming surface 211S with respect to theetching rate of the particles M₁ is preferably 25% or less. The ratio ofthe etching rate of the light emitting structure forming surface 211Swith respect to the etching rate of the particles M₁ is more preferably15% or less, and particularly preferably 10% or less. It should be notedthat for such etching conditions, the etching gas used in the reactiveetching may be selected appropriately. For example, when the devicesubstrate 211B is sapphire and the particles M₁ are silica, one or moregases selected from the group consisting of CF₄, SF₆, CHF₃, C₂F₆, C₃F₈,CH₂F₂, O₂ and NF₃ may be used as an etching gas.

[Etching Step of Light Emitting Structure Forming Surface 211S]

As shown in FIG. 12, in the etching step, the light emitting structureforming surface 211S is etched by using the particles M₁ with a reduceddiameter as a mask. At this time, in the light emitting structureforming surface 211S, the first exposed portion S21 is exposed to aplasma of the etching gas through a void surrounded by three particlesM₁ that are adjacent to each other. In the light emitting structureforming surface 211S, the second exposed portion S22 is exposed to theplasma of the etching gas through a void between the two particles M₁that are adjacent to each other. Then, the particles M₁ constituting amonolayer particle film are also exposed to the plasma of the etchinggas.

Here, a first region 214 that combines the first exposed portion S21 andthe second exposed portion S22 located in the periphery of the firstexposed portion S21 has a larger area than a second region 213 that addstogether the second exposed portions S22 that are voids between the twoparticles M₁ that are adjacent to each other. Therefore, the etchingrate of the first region 214 is greater than the etching rate of thesecond region 213. For this reason, in the light emitting structureforming surface 211S, the etching of the first region 214 advancesfaster than the etching of the second region 213. In addition, in thelight emitting structure forming surface 211S, the etching of the secondregion 213 advances faster than the etching of a portion covered withthe particles M₁. Further, among a plurality of first regions 214, theetching rate in the first region 214 increases as the size of the firstregion 214 increases. In addition, among a plurality of second regions213, the etching rate in the second region 213 increases as the size ofthe second region 213 increases.

As a result, in the light emitting structure forming surface 211S, aflat portion 214 is formed in the first region 214 as a deep recessedportion. In addition, as a recessed portion shallower than the flatportion 214, a bridge portion 213 is formed in the second region 213.Further, as a portion other than the flat portion 214 and the bridgeportion 213, a convex portion 212 having a hemispherical shape isformed. Among a plurality of bridge portions 213, the larger thedistance between the convex portions 212 that are connected by thebridge portion 213, the height of the bridge portion 213 is lowered.When the bridge portions are actively produced, for example, in the caseof a combination of the silica particle mask and the sapphire substrate,the interval between the convex portions 212 becomes 300 nm to 700 nmwhen the most frequent pitch is 3.0 μm, and the height of the bridge inthat case is 10 to 300 nm. In addition, the interval between the convexportions 212 becomes 10 nm to 100 nm when the most frequent pitch is 400nm, and the height of the bridge in that case is 5 nm to 100 nm. Inaddition, since the spacing between the convex portions 212 and theheight of the bridge change by dry etching conditions includingcombinations of the material of the particle mask and the material ofthe substrate and the selection of gas, the above values vary dependingon the conditions.

It should be noted that when the size of the second exposed portion S22is changed in the etching step of the monolayer particle film F₁described above, in the subsequent etching step of the light emittingstructure forming surface 211S, the height of the bridge portion 213 tobe finally formed changes. For the method of changing the height of thebridge portion 213, in addition to the etching step of the monolayerparticle film F₁, a change in the etching gas used in etching of thelight emitting structure forming surface 211S can be mentioned.

For example, a gas that increases the etching rate of the monolayerparticle film F₁ while decreasing the etching rate of the devicesubstrate 211B is used for the etching step of the light emittingstructure forming surface 211S. At this time, the etching rate of theparticles M₁ is further reduced with respect to the light emittingstructure forming surface 211S, and the rate of expansion of the secondexposed portion S22 is also further reduced. Eventually, a largedifference occurs between the degree of progress of etching in the firstexposed portion S221 and the degree of progress of etching in the secondexposed portion S22, and, as a result, the height of the bridge portion213 is increased.

On the other hand, a gas that decreases the etching rate of themonolayer particle film F₁ while increasing the etching rate of thedevice substrate 211B is used for an etching gas of the light emittingstructure forming surface 211S. At this time, the etching rate of theparticles M₁ becomes close with respect to the light emitting structureforming surface 211S, and the rate of expansion of the second exposedportion S22 is further increased. Eventually, a difference between thedegree of progress of etching in the first exposed portion S221 and thedegree of progress of etching in the second exposed portion S22 becomessmall, and, as a result, the height of the bridge portion 213 islowered. It should be noted that the gas used at this time may becomposed of one type of gas, or may be composed of two or more types ofgases.

Furthermore, in the etching step of the monolayer particle film F₁described above, a change in the height of the bridge portion 213 may becombined with the change in the height of the bridge portion 213 due tothe change in the etching gas as described above.

It should be noted that even if the bridge portions are not activelyproduced (even if the height of the bridge portion corresponds tovirtually zero), by the effect of extending the interval between theconvex portions 212 due to the reduction in the particle size of themask as described above, it is possible to secure more area of the flatportion required in the LED deposition step, and more efficientepitaxial crystal growth with less crystal defects can be achieved.Therefore, as a result, a benefit of improving the emission efficiencyof the semiconductor light emitting device fabricated by depositing asemiconductor layer on such a substrate can be attained.

The pitch of the convex portion 212 is equivalent to the spacing betweenthe particles M₁ that are adjacent to each other, and the arrangement ofthe convex portion 212 is also similar to the arrangement of theparticles M₁. In addition, the arrangement of the bridge portion 213 ison a line connecting the centers of the particles M₁ that are adjacentto each other, and the shape of the bridge portion 213 is a linear shapeconnecting the centers of the particles M₁ that are adjacent to eachother. Further, of the light emitting structure forming surface 211S, aconvex portion team TL2 is formed in a portion where the film elementsof the monolayer particle film are stacked, and a convex portion groupTG2 is formed in a portion where the hexagonal packing structures of theparticles M₁ are stacked.

In the etching step, the etching rate of the light emitting structureforming surface 211S is preferably higher than the etching rate of theparticles M₁. The ratio of the etching rate of the light emittingstructure forming surface 211S with respect to the etching rate of theparticles M₁ is preferably at least 200%, and more preferably 300% orless. It should be noted that for such etching conditions, the etchinggas used in the reactive etching may be selected appropriately. Forexample, when the device substrate 211B is sapphire and the particles M₁are silica, one or more gases selected from the group consisting of Cl₂,BCl₃, SiCl₄, HBr, HI and HCl may be used as an etching gas.

[Semiconductor Light Emitting Device]

As shown in FIG. 13, a semiconductor light emitting device 200 includesa device substrate 211B as a base material. The semiconductor lightemitting device 200 includes, in the light emitting structure formingsurface 211S of the device substrate 211B, a light emitting structure221 that covers an uneven structure of the light emitting structureforming surface 211S. The light emitting structure 221 includes alaminated body constituted of a plurality of semiconductor layers andemits light by recombining carriers by the supply of electric current.Each of the plurality of semiconductor layers is laminated sequentiallyfrom the light emitting structure forming surface 211S.

The semiconductor light emitting device 200 can employ the sameconfiguration as that of the semiconductor light emitting devicedescribed in the first embodiment. In addition, the semiconductor lightemitting device 200 can be formed by the method described in the firstembodiment.

According to the present embodiment, the following effects can beobtained.

(1) The total reflection by the light emitting structure forming surface211S can be suppressed by the geometric optical effects (reflection andrefraction) in the bridge portion 213. For this reason, the efficiencyof extracting light generated by the light emitting structure 221 can beenhanced.

(2) Since a plurality of bridge portions 213 are connected to one convexportion 212, as compared with a configuration in which one bridgeportion 213 is connected to one convex portion 212, the effect inaccordance with the above effect (1) can be further enhanced.

(3) Since a convex portion group TG2 has a hexagonal packing structureand the bridge portions 213 is connected to each of the convex portions212 constituting the hexagonal packing structure, the effect inaccordance with the above effect (1) can be further enhanced.

(4) Since the arrangement of the convex portion 212 has a randomness, inthe plane of the light emitting structure forming surface 211S, theuniformity of the effect in accordance with the above effect (1) can beenhanced.

(5) Since the top surface 213T of the bridge portion 213 is a crystalplane, the lack of growth of the semiconductor layer due to theformation of the convex portion 212 can be suppressed.

(6) By etching for widening the void between the particles M₁ that areadjacent to each other, the second exposed portion S22 for forming thebridge portion 213 is formed. For this reason, one monolayer particlefilm F₁ functions as a mask for forming the convex portion 212 and theflat portion 214, and as a mask for forming the bridge portion 213. As aresult, compared to a method that requires the mask for forming theconvex portion 212 and the mask for forming the bridge portion 213separately, the number of steps required for the manufacture of thedevice substrate 211B is reduced.

It should be noted that the present embodiment can also be modified andimplemented as follows.

The monolayer particle film F₁ may include, in advance, before beingtransferred to the light emitting structure forming surface 211S, a voidfor partitioning the first exposed portion S221 and a void for formingthe second exposed portion S22. In accordance with such a configuration,a step of selectively etching the monolayer particle film F₁ will beomitted.

As shown on the left side of FIG. 14, the top surface 213T of the bridgeportion 213 may be a concave surface recessed toward the flat portion214, as viewed from a direction that intersects with the direction towhich the bridge portion 213 connects. In short, the bridge portion 213may be a portion having a lower height than the height of the convexportion 212 and connecting portions of the convex portions 212 that areadjacent to each other.

As shown on the left side of FIG. 15, the top surface 213T of the bridgeportion 213 may be a concave surface recessed toward the flat portion214, as viewed from a direction that intersects with the direction towhich the bridge portion 213 connects, and, as shown on the right sideof FIG. 15, may also be a convex surface protruding from the flatportion 214, as viewed from a direction in which the bridge portion 213continues. In short, the top surface 213T of the bridge portion 213 maynot be a crystal plane.

The flat portion 214 may be surrounded by four or more convex portionpairs TP2. Furthermore, the flat portion 214 may not be surrounded bythe convex portion pair TP2. For example, in the direction thatintersects with the direction to which the bridge portion 213 connects,it may have a structure in which two flat portions 214 sandwich onebridge portion 213.

In a convex portion pair TP2 in which the intervals between the convexportions 212 that are adjacent to each other are different from eachother, the height of the bridge portion 213 may be equal to each other.

The semiconductor light emitting device substrate of the presentembodiment includes a light emitting structure forming surface on whicha light emitting structure including a semiconductor layer is formed,the aforementioned light emitting structure forming surface includes aflat portion that spreads along one crystal plane, two convex portionsthat are protruded from the aforementioned flat portion and one bridgeportion that is protruded from the aforementioned flat portion, theamount that protrudes from the aforementioned flat portion is smaller inthe bridge portion than in the aforementioned convex portion, theaforementioned two convex portions are connected by the aforementionedone bridge portion, the most frequent pitch of the aforementioned convexportion is equal to or more than 100 nm and equal to or less than 5 μm,and the aspect ratio of the aforementioned large number of the convexportions may be from 0.5 to 1.0.

The semiconductor light emitting device substrate of the presentembodiment includes a light emitting structure forming surface on whicha light emitting structure including a semiconductor layer is formed,the aforementioned light emitting structure forming surface includes aflat portion that spreads along one crystal plane, two convex portionsthat are protruded from the aforementioned flat portion and one bridgeportion that is protruded from the aforementioned flat portion, theamount that protrudes from the aforementioned flat portion is smaller inthe bridge portion than in the aforementioned convex portion, theaforementioned two convex portions are connected by the aforementionedone bridge portion, the most frequent pitch of the aforementioned convexportion is equal to or more than 100 nm and equal to or less than 1 μm,and the aspect ratio of the aforementioned large number of the convexportions may be from 0.5 to 1.0.

The semiconductor light emitting device substrate of the presentembodiment includes a light emitting structure forming surface on whicha light emitting structure including a semiconductor layer is formed,the aforementioned light emitting structure forming surface includes aflat portion that spreads along one crystal plane, two convex portionsthat are protruded from the aforementioned flat portion and one bridgeportion that is protruded from the aforementioned flat portion, theamount that protrudes from the aforementioned flat portion is smaller inthe bridge portion than in the aforementioned convex portion, theaforementioned two convex portions are connected by the aforementionedone bridge portion, the most frequent pitch of the aforementioned convexportion is from 200 nm to 700 nm, and the aspect ratio of theaforementioned large number of the convex portions may be from 0.5 to1.0.

The semiconductor light emitting device substrate of the presentembodiment includes a light emitting structure forming surface on whicha light emitting structure including a semiconductor layer is formed,the aforementioned light emitting structure forming surface includes aflat portion that spreads along one crystal plane, two convex portionsthat are protruded from the aforementioned flat portion and one bridgeportion that is protruded from the aforementioned flat portion, theamount that protrudes from the aforementioned flat portion is smaller inthe bridge portion than in the aforementioned convex portion, theaforementioned two convex portions are connected by the aforementionedone bridge portion, the most frequent pitch of the aforementioned convexportion is equal to or more than 100 nm and equal to or less than 5 μm,the aspect ratio of the aforementioned large number of the convexportions is from 0.5 to 1.0, and the length along the longitudinaldirection of the bridge portion may be equal to or more than 50 nm andequal to or less than 300 nm.

The semiconductor light emitting device substrate of the presentembodiment includes a light emitting structure forming surface on whicha light emitting structure including a semiconductor layer is formed,the aforementioned light emitting structure forming surface includes aflat portion that spreads along one crystal plane, two convex portionsthat are protruded from the aforementioned flat portion and one bridgeportion that is protruded from the aforementioned flat portion, theamount that protrudes from the aforementioned flat portion is smaller inthe bridge portion than in the aforementioned convex portion, theaforementioned two convex portions are connected by the aforementionedone bridge portion, the most frequent pitch of the aforementioned convexportion is equal to or more than 100 nm and equal to or less than 5 μm,the aspect ratio of the aforementioned large number of the convexportions is from 0.5 to 1.0, and the length along the short direction ofthe bridge portion may be equal to or more than 10 nm and equal to orless than 100 nm.

The semiconductor light emitting device substrate of the presentembodiment includes a light emitting structure forming surface on whicha light emitting structure including a semiconductor layer is formed,the aforementioned light emitting structure forming surface includes aflat portion that spreads along one crystal plane, two convex portionsthat are protruded from the aforementioned flat portion and one bridgeportion that is protruded from the aforementioned flat portion, theamount that protrudes from the aforementioned flat portion is smaller inthe bridge portion than in the aforementioned convex portion, theaforementioned two convex portions are connected by the aforementionedone bridge portion, the most frequent pitch of the aforementioned convexportion is equal to or more than 100 nm and equal to or less than 5 μm,the aspect ratio of the aforementioned large number of the convexportions may be from 0.5 to 1.0, and the bridge portion height may belower than half the height of the convex portion. In addition, thebridge portion height may be substantially zero, and, in this case, byadjusting such that the distance between the aforementioned two convexportions widens by the reduction in particle size and increasing theexposed portion of the c-plane of sapphire crystal that can be thestarting point of epitaxial growth, it is possible to contribute toperforming deposition of high quality with a low crystal dislocationdensity in the LED deposition step and obtaining a highly efficient LEDlight emitting device.

The semiconductor light emitting device substrate of the presentembodiment is a semiconductor light emitting device substrate having anuneven structure on one surface of the substrate, the aforementioneduneven structure has a large number of convex portions and a flatsurface between each of the convex portions, and also has a plurality ofareas in which the central points of seven adjacent convex portions arealigned continuously in a positional relationship so as to become thesix vertices and point of intersection of diagonal lines of a regularhexagon, the area, shape and lattice orientation of the aforementionedplurality of areas are random, the aspect ratio of the aforementionedlarge number of convex portions is from 0.5 to 1.0, and the length ofthe flat surfaces f1 l to f1 n when viewed in a cross section thatpasses through the vertex of the convex portion and is perpendicular tothe aforementioned substrate may be from 5% to 40% with respect to astraight line connecting the vertices of the two adjacent convexportions among the convex portions c1 l to c1 n.

The semiconductor light emitting device substrate of the presentembodiment is a semiconductor light emitting device substrate having anuneven structure on one surface of the substrate, the aforementioneduneven structure has a large number of convex portions and a flatsurface between each of the convex portions, and also has a plurality ofareas in which the central points of seven adjacent convex portions arealigned continuously in a positional relationship so as to become thesix vertices and point of intersection of diagonal lines of a regularhexagon, the area, shape and lattice orientation of the aforementionedplurality of areas are random, the aspect ratio of the aforementionedlarge number of convex portions is from 0.5 to 1.0, and the length ofthe flat surfaces f1 l to f1 n when viewed in a cross section thatpasses through the vertex of the convex portion and is perpendicular tothe aforementioned substrate may be from 15% to 25% with respect to astraight line connecting the vertices of the two adjacent convexportions among the convex portions c1 l to c1 n.

EXAMPLES Example 1

<Production of Semiconductor Light Emitting Device>

On a sapphire substrate having a diameter of 2 inches and a thickness of0.42 mm, SiO₂ colloidal silica particles having a diameter of φ3 μm werecoated as a monolayer by a monolayer coating method disclosed inJapanese Patent Application No. 2008-522506.

More specifically, a 3.0% by mass aqueous dispersion (dispersion liquid)of spherical colloidal silica of SiO₂ colloidal silica particles havingan average particle size of 3.02 μm (coefficient of variation ofparticle size=0.85%) was prepared.

Then, brominated hexadecyltrimethylammonium (surfactant) having aconcentration of 50% by mass was added to the dispersion liquid so as tobe 2.5 mmol/L, and the resultant was stirred for 30 minutes to adsorbthe brominated hexadecyltrimethylammonium onto the surface of thecolloidal silica particles. At this time, the dispersion liquid and thebrominated hexadecyltrimethylammonium were mixed so that the mass of thebrominated hexadecyltrimethylammonium was 0.04 times the mass of thecolloidal silica particles.

Then, to the resulting dispersion liquid, chloroform having the samevolume as the volume of the dispersion liquid was added and stirredthoroughly, and the hydrophobized colloidal silica was extracted by oilphase extraction.

The thus obtained dispersion liquid of hydrophobized colloidal silicahaving a concentration of 1.5% by mass was added dropwise at a droppingrate of 0.01 ml/sec to a liquid surface (water was used as underlyingwater, at a water temperature of 25° C.) in a water tank (LB troughunit) equipped with a surface pressure sensor for measuring the surfacepressure of a monolayer particle film and a movable barrier forcompressing the monolayer particle film in a direction along the liquidsurface. It should be noted that in the underlying water in the watertank, the sapphire substrate described above had been immersed inadvance.

From during the dropwise addition, while ultrasonic wave (output: 120 W,frequency: 1.5 MHz) was irradiated from the underlying water toward thesurface of the water to facilitate closest packing of particlestwo-dimensionally, chloroform serving as a solvent of the dispersionliquid was volatilized to form a monolayer particle film.

Then, the monolayer particle film was compressed using the movablebarrier until a diffusion pressure of 18 mNm⁻¹ was achieved, thesapphire wafer was pulled upward at a rate of 5 mm/min, and themonolayer particle film was transferred onto one side of the substrate,thereby obtaining a sapphire wafer provided with a monolayer particlefilm etching mask constituted of colloidal silica.

Dry etching was carried out for reducing the particle size of themonolayer particle film etching mask constituted of colloidal silica onthe thus obtained sapphire wafer. More specifically, under theconditions of an antenna power of 1,500 W, a bias of 80 W and a pressureof 5 Pa, SiO₂ particles having an average particle size of 3.02 μm as aninitial value were reduced in size in a CF₄ gas so that an averageparticle size after the treatment was 2.80 μm.

Subsequently, dry etching for processing the sapphire wafer serving as abase material was carried out. More specifically, under the conditionsof an antenna power of 1,500 W, a bias of 300 W, a pressure of 1 Pa anda temperature inside an etching chamber of 80 to 110° C., the SiO₂mask/sapphire substrate was processed by dry etching in a Cl₂ gas toobtain a sapphire substrate for a semiconductor light emitting deviceprovided with an uneven structure constituted by having a most frequentpitch of 3 μm, a structure height of 1.5 μm, a flat portion distance of0.4 μm, a length of a portion corresponding to a bridge portion of 0.4μm and a height of the portion corresponding to the bridge portion of 3nm or less (the bridge portion was flat since the bridge portion did nothave a substantial height), as shown in Table 1.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, an n-type semiconductorlayer, an active layer and a p-type semiconductor layer weresequentially laminated, followed by formation of a p-electrode andn-electrode to complete the semiconductor light emitting device. Each ofGaN-based semiconductor layers was formed by the MOCVD (Metal OrganicChemical Vapor Deposition) method, which was generally widely used. Inthe MOCVD method, ammonia gas and an alkyl compound gas of a group IIIelement, such as trimethyl gallium, trimethyl ammonium and trimethylindium were supplied onto a sapphire substrate at a temperatureenvironment of 700° C. to 1,000° C. to allow a thermal decompositionreaction, thereby depositing the desired crystal by epitaxial growth onthe substrate.

As the configuration of the n-type semiconductor layer, 15 nm ofAl_(0.9)Ga_(0.1)N as a low-temperature growth buffer layer, 4.5 μm ofundoped GaN, 3 μm of Si-doped GaN as an n-cladding layer and 250 nm ofundoped GaN were sequentially laminated.

Since the active layer increases the probability of recombination, amultiple quantum well for improving the internal quantum efficiency wasformed by sandwiching several layers with a narrow band gap. As theconstitution thereof, an undoped In_(0.15)Ga_(0.85)N (quantum welllayer) and Si-doped GaN (barrier layer) were deposited alternately witha film thickness of 4 nm and 10 nm, respectively, so that 9 layers ofthe undoped In_(0.15)Ga_(0.85)N and 10 layers of the Si-doped GaN werelaminated.

As the p-type semiconductor layer, 15 nm of Mg-doped AlGaN, 200 nm ofundoped GaN and 15 nm of Mg-doped GaN were laminated.

In a region for forming the n-type electrode, from the Mg-doped GaNserving as the p-type semiconductor layer in the outermost layer to theundoped GaN serving as the n-type semiconductor layer were removed byetching to expose the Si-doped GaN layer. An n-type electrode composedof Al and W was formed on the exposed surface, and an n-pad electrodecomposed of Pt and Au was formed on the n-type electrode.

A p-electrode composed of Ni and Au was formed on the entire surface ofthe p-type semiconductor layer, and a p-pad electrode composed of Au wasformed on the p-electrode.

A semiconductor device (the size of one device was 300 μm×350 μm) in abare chip state was formed by the above operation.

Comparative Example 1

After spin-coating a photoresist at a thickness of 750 nm on a sapphiresubstrate with a diameter of 2 inches and a thickness of 0.42 mm anddrawing a mask having a pitch of 3 μm by a laser lithography method,fine processing by dry etching was performed to obtain a sapphiresubstrate for a semiconductor light emitting device provided with anuneven structure constituted by having a most frequent pitch of 3 μm, astructure height of 1.5 μm and a flat portion distance of 0.4 μm, asshown in Table 1.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

Example 2

With the exception that SiO₂ colloidal silica particles having anaverage particle size of 305 nm (coefficient of variation of particlesize=3.4%) were used and the thickness of the undoped GaN serving as then-type semiconductor layer was changed to 2.5 μm, fine processing by theparticle mask method was performed in the same manner as in Example 1 toobtain a sapphire substrate for a semiconductor light emitting deviceprovided with an uneven structure constituted by having a most frequentpitch of 300 nm, a structure height of 150 nm, a flat portion distanceof 40 nm, a length of a portion corresponding to a bridge portion of 30nm and a height of the portion corresponding to the bridge portion of 3nm or less (the bridge portion was flat since the bridge portion did nothave a substantial height), as shown in Table 1.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

Comparative Example 2

After spin-coating a photoresist at a thickness of 100 nm on a sapphiresubstrate with a diameter of 2 inches and a thickness of 0.42 mm anddrawing a mask having a pitch of 300 nm by an electron beam lithographymethod, fine processing by dry etching was performed to obtain asapphire substrate for a semiconductor light emitting device providedwith an uneven structure constituted by having a most frequent pitch of300 nm, a structure height of 150 nm and a flat portion distance of 40nm, as shown in Table 1.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

<Evaluation Method>

The semiconductor light emitting devices (bare chips before beingembedded in a resin) obtained in each of Examples and ComparativeExamples that were still in the form of the bare chips were mounted on asmall prober (sp-0-2Ls manufactured by ESS Tech, Inc.), and were turnedon at a drive current of 20 to 40 mA using an open probe, and thefollowing evaluations were carried out. The results are shown in Table1.

[In-plane Radiation Anisotropy]

The semiconductor light emitting device was mounted and lit on arotating stage of PR50CC manufactured by Newport Corporation. Whilerotating the rotating stage 360 degrees at 0.5°/sec around the Z axis,the brightness was measured continuously using a CCD camera (luminancemeter BM7A manufactured by Topcon Corporation) from a position at whichan elevation angle was 30 degrees and a distance was 150 mm from a lightemitting surface of the semiconductor light emitting device.

A curve obtained by plotting the measurement results on a graph havingthe brightness on a vertical axis and rotation angle on a horizontalaxis and a straight line of the brightness average value from 0 to 360degrees were drawn to overlap, and the in-plane radiation anisotropy wasdetermined from the following equation.In-plane radiation anisotropy=(sum of the area enclosed by the curve andthe straight line)/(average value×360 degrees)

Semiconductor light emitting devices having a large value for thein-plane radiation anisotropy exhibit radiation characteristics of highanisotropy and low uniformity with respect to the radiation in thein-plane direction. Conversely, semiconductor light emitting deviceshaving a small value for the in-plane radiation anisotropy exhibitradiation characteristics of low anisotropy and high uniformity withrespect to the radiation in the in-plane direction.

[External Quantum Efficiency]

In order to confirm the effect of improving the light extractionefficiency, the external quantum efficiency was measured using aSpectraflect integrating sphere and CDS-600-type spectroscopemanufactured by Labsphere, Inc.

TABLE 1 Ratio of maximum Improvement rate Most value and minimum oflight extraction Mask production frequent Structure Flat portion valueof FFT In-plane efficiency (external method pitch P height distance ffundamental wave anisotropy quantum efficiency) Ex. 1 Particle coating 3μm 1.5 μm 0.4 μm  1.15-fold 4.1% 52% Comp. Ex. 1 Photolithography 3 μm1.5 μm 0.4 μm 32.50-fold 9.0% 53% Ex. 2 Particle coating 300 nm 150 nm40 nm  1.05-fold 2.9% 87% Comp. Ex. 2 Interference 300 nm 150 nm 40 nm40.15-fold 11.6% 84% exposure

In Table 1, the flat portion distance shows an average value of thewidth of a flat surface present between the central points of theadjacent convex portions.

As shown in Table 1, in Example 1 and in Example 2, low in-planeradiation anisotropy was confirmed. On the other hand, in ComparativeExample 1 prepared by the photolithography method and in ComparativeExample 2 prepared by an interference exposure method, high in-planeradiation anisotropy was confirmed. From these results, it was foundthat according to the present invention, in a simpler method thanconventional methods, a sufficient light extraction efficiency and lowin-plane radiation anisotropy can be achieved.

Example 3

With the exception that a sapphire substrate having a TTV of 6.66 μm, aWARP of 17.06 μm and a |BOW| of 11.98 μm was used, in the same manner asin Example 1, fine processing by the particle mask method was performedto obtain a sapphire substrate for a semiconductor light emitting deviceprovided with an uneven structure constituted by having a most frequentpitch of 3 μm, a structure height of 1.5 μm and a flat portion distanceof 0.4 μm, as shown in Table 2. In addition, when each of 20 samplingpositions was extracted from the central portion of the substrate andthe outer periphery portion, and the shape of the convex portion wasmeasured to determine the coefficient of variation H′, the values of1.77 and 2.12 were obtained, respectively.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

Comparative Example 3

With the exception that a sapphire substrate having a TTV of 5.24 μm, aWARP of 17.31 μm and a |BOW| of 11.07 μm was used, in the same manner asin Comparative Example 1, after producing a circular mask having a pitchof 3 μm using a laser lithography method, fine processing by dry etchingwas performed to obtain a sapphire substrate for a semiconductor lightemitting device provided with an uneven structure constituted by havinga most frequent pitch of 3 μm, a structure height of 1.5 μm and a flatportion distance of 0.4 μm, as shown in Table 2. In addition, for thecoefficients of variation H′ of the convex portions in the centralportion of the substrate and the outer peripheral portion, the values of4.82 and 10.45 were obtained, respectively.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

Example 4

With the exception that a sapphire substrate having a TTV of 5.89 μm, aWARP of 18.78 μm and a |BOW| of 11.02 μm was used, fine processing bythe particle mask method was performed in the same manner as in Example2 to obtain a sapphire substrate for a semiconductor light emittingdevice provided with an uneven structure constituted by having a mostfrequent pitch of 300 nm, a structure height of 150 nm and a flatportion distance of 40 nm, as shown in Table 1. In addition, for thecoefficients of variation H′ of the convex portions in the centralportion of the substrate and the outer peripheral portion, the values of2.51 and 2.68 were obtained, respectively.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

Comparative Example 4

With the exception that a sapphire substrate having a TTV of 5.56 μm, aWARP of 18.57 μm and a |BOW| of 10.85 μm was used, in the same manner asin Comparative Example 2, after drawing a circular mask having a pitchof 300 nm by an electron beam lithography method, fine processing by dryetching was performed to obtain a sapphire substrate for a semiconductorlight emitting device provided with an uneven structure constituted byhaving a most frequent pitch of 300 nm, a structure height of 150 nm anda flat portion distance of 40 nm, as shown in Table 1. In addition, forthe coefficients of variation H′ of the convex portions in the centralportion of the substrate and the outer peripheral portion, the values of5.09 and 10.13 were obtained, respectively.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

<Evaluatiton Method>

For the semiconductor light emitting devices (bare chips before beingembedded in a resin) obtained in each of Examples and ComparativeExamples, each of 20 points was extracted from the central portion ofthe substrate and the outer periphery portion, and still in the form ofthe bare chips, they were mounted on a small prober (sp-0-2Lsmanufactured by ESS Tech, Inc.), and were turned on at a drive currentof 20 to 40 mA using an open probe, and the following evaluations werecarried out. The results are shown in Table 2.

[External Quantum Efficiency]

In order to confirm the effect of improving the light extractionefficiency, the external quantum efficiency was measured using aSpectratlect integrating sphere and CDS-600-type spectroscopemanufactured by Labsphere, Inc.

TABLE 2 Most Flat Mask production frequent Structure portion methodpitch P height distance f TTV WARP |BOW| Ex. 3 Particle coating 3 μm 1.5μm 0.4 μm 6.66 μm 17.06 μm 11.98 μm Comp. Ex. 3 Photolithography 3 μm1.5 μm 0.4 μm 5.24 μm 17.31 μm 11.07 μm Ex. 4 Particle coating 300 nm150 nm 40 nm 5.89 μm 18.78 μm 11.02 μm Comp. Ex. 4 Interference 300 nm150 nm 40 nm 5.56 μm 18.57 μm 10.85 μm exposure In-plane central portion(N = 20) In-plane outer peripheral portion (N = 20) ImprovementImprovement rate of light rate of light extraction efficiency extractionefficiency Coefficient of (external quantum Standard Coefficient of(external quantum Standard variation H′ efficiency) deviation variationH′ efficiency) deviation Ex. 3 1.77 53% 0.35 2.12 52% 0.34 Comp. Ex. 34.82 48% 0.45 10.45 40% 1.60 Ex. 4 2.51 86% 0.89 2.68 84% 0.93 Comp. Ex.4 5.09 78% 1.46 10.13 69% 2.14

In Table 2, it is shown that the larger the coefficient of variation H′of the convex portions, the less the in-plane uniformity of the unevenstructure on the sapphire substrate is maintained, and also the standarddeviation indicates variations in the improvement rate of the lightextraction efficiency at each measurement position.

As shown in Table 2, in Example 3 and Example 4, in both the centralportion and the outer periphery portion within the plane, since thecoefficients of variation H′, the improvement rates of the lightextraction efficiency and the standard deviations of the improvementrate of the light extraction exhibit substantially the same value, itwas confirmed that the in-plane uniformity of the uneven structure onthe sapphire substrate was high. On the other hand, in ComparativeExample 3 prepared by the photolithography method and in ComparativeExample 4 prepared by an interference exposure method, it was confirmedthat there was a large difference in the above values in the centralportion and the outer peripheral portion within the plane. From theseresults, according to Examples 3 and 4, even if a substrate having arelatively low flatness with a TTV of 5 μm to 30 μm, a WARP of 10 μm to50 μm and a |BOW| of 10 μm to 50 μm was used, it was found that in-planeuniformity of the uneven structure was maintained with high accuracy anda sufficient light extraction efficiency could be achieved.

Example 5

With the exception that SiO₂ colloidal silica particles having anaverage particle size of 1.06 μm (coefficient of variation of particlesize=3.1%) were used and the thickness of the undoped GaN serving as then-type semiconductor layer was changed to 4.0 μm, fine processing by theparticle mask method was performed in the same manner as in Example 1 toobtain a sapphire substrate for a semiconductor light emitting deviceprovided with an uneven structure constituted by having a most frequentpitch of 1.0 μm, a structure height of 510 nm, a length of the bridgeportion of 280 nm and a height of the bridge portion of 106 nm, as shownin Table 1.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

Comparative Example 5

After spin-coating a photoresist at a thickness of 300 nm on a sapphiresubstrate with a diameter of 2 inches and a thickness of 0.42 mm anddrawing a mask having a pitch of 1 μm by a laser lithography method,fine processing by dry etching was performed to obtain a sapphiresubstrate for a semiconductor light emitting device provided with anuneven structure constituted by having a most frequent pitch of 1 μm, astructure height of 500 μm and a flat portion distance of 290 nm, asshown in Table 3.

On the uneven structure surface of the thus obtained sapphire substratefor a semiconductor light emitting device, the n-type semiconductorlayer, active layer and p-type semiconductor layer that had the sameconfigurations as those in Example 1 were sequentially laminated,followed by formation of a p-electrode and n-electrode to complete thesemiconductor light emitting device (the size of one device was 300μm×350 μm).

<Evaluation Method>

The semiconductor light emitting devices (bare chips before beingembedded in a resin) obtained in each of Examples and ComparativeExamples that were still in the form of the bare chips were mounted on asmall prober (sp-0-2Ls manufactured by ESS Tech, Inc.), and were turnedon at a drive current of 20 to 40 mA using an open probe, and thefollowing evaluations were carried out. The results are shown in Table3.

[External Quantum Efficiency]

In order to confirm the effect of improving the light extractionefficiency, the external quantum efficiency was measured using aSpectraflect integrating sphere and CDS-600-type spectroscopemanufactured by Labsphere, Inc.

TABLE 3 Distance of Improvement location rate of light Mostcorresponding extraction efficiency Mask production frequent Structureto bridge Bridge (external quantum method pitch P height portion heightefficiency) Ex. 5 Particle coating 1 μm 510 nm 280 nm 106 nm 65% Comp.Ex. 5 Photolithography 1 μm 500 nm 290 nm  0 nm 59%

As shown in Table 3, since the bridge portion is provided in the finestructure in Example 5, the external quantum efficiency is about 10%higher as compared to Comparative Example 5 where the bridge portion isabsent. It is interpreted that in Example 5, this is because the lightconfined inside the LED element becomes a waveguide mode and scattersdue to the presence of the bridge portion to be taken out from the lightextraction surface. On the other hand, in Comparative Example 5 wherethe bridge portion is absent, because there is no light extractioneffect as described above, the external quantum efficiency is poor.

[Industrial Applicability]

A semiconductor light emitting device substrate in which crystal defectsin the semiconductor layer are less likely to occur, a sufficient lightextraction efficiency is achieved and the color shift is also preventedis provided by a simple method.

[Reference Signs List]

11: Semiconductor light emitting device substrate; C1: Area; c11: Convexportion; f11: Flat surface; t11: Central point; S1: Substrate; M1:Particle; F1: Monolayer particle film; W1: Underlying water; V1: Watertank; S21: First exposed portion; S22: Second exposed portion; TP2:Convex portion pair; TG2: Convex portion group; TL2: Convex portionteam; 211B: Device substrate; 211S: Light emitting structure formingsurface; 212: Convex portion; 213: Bridge portion; 213T: Top surface;214: flat portion; 221: Light emitting structure

What is claimed is:
 1. A semiconductor light emitting device substrate which is a semiconductor light emitting device substrate including an uneven structure on one surface of the substrate, wherein said uneven structure comprises numerous convex portions and a flat surface between the convex portions, and a bridge connecting between said convex portions, and also has a plurality of areas in which the central points of seven adjacent convex portions are aligned continuously in a positional relationship so as to become six vertices and intersection point of diagonal lines of a regular hexagon, and an area, shape and lattice orientation of said plurality of areas are random.
 2. A semiconductor light emitting device comprising: the conductor light emitting device substrate described in claim 1; and a semiconductor functional layer laminated on said semiconductor light emitting device substrate, wherein said semiconductor functional layer comprises at least a light emitting layer, and a wavelength conversion layer for converting a wavelength of light emitted from said light emitting layer to a long wavelength side than a wavelength of said light, in a light extraction side of said semiconductor functional layer.
 3. The semiconductor light emitting device according to claim 2, wherein said wavelength conversion layer comprises a blue phosphor emitting fluorescence with a peak wavelength of 410 nm to 483 nm, a green phosphor emitting fluorescence with a peak wavelength of 490 nm to 556 nm, and a red phosphor emitting fluorescence with a peak wavelength of 585 nm to 770 nm.
 4. The semiconductor light emitting device according to claim 3, wherein said wavelength conversion layer includes a yellow phosphor emitting fluorescence with a peak wavelength of 570 nm to 578 nm. 